KittyPlaut

@maxhgns provides some very good advice. However it is worth noting that given the notorious competitiveness of philosophy PhD admissions, the old idiom "one bird in hand is better than two in the bush" may be applicable. Not that such a warning should be decisive, but I wouldn't dismiss it too easily either. You have an admission to a PhD program, and there is no guarantee that you will be equally successful next time (of course it's also possible you're much more successful the second time around).

Unfortunately the answer is a cold hard no. If you back out now a call will be put out for your detainment by the Inter-university Police. You will be found and held, forced to finish the terms of your accepted offer. At the conclusion of these terms, you will be placed in a black list among all degree granting institutions barring your employment there on grounds of disrespect to the high authority of the Ivory Tower.
 
You ought to think these things through beforehand...

I ended up taking the gap year (I wasn't where I had to be academically during my senior year) and a lot of the worries you have about finding a job in the meantime ring true. I'm not sure how much you've done throughout undergrad that might make starting a career feasible, but it's pretty tough to search for jobs and work on applications, not to mention searching for jobs and, as you said, lying about a professional trajectory that you don't intend to follow-through on.
I would definitely speak with your advisors to see what they think about applying this Fall. It would likely involve a lot of work over the summer, but imo it's absolutely worth it if you know you want to go on to grad school and know what your areas of interest would be.

They're full of shit. People in grad school are always posturing about how hard they work, but that's all it is. They've got some screwed up idea of what the perfect grad student is, and they constantly fail to meet it, and it wreaks havoc with their brain chemistry. 
Being a good student really isn't inconsistent with maintaining a healthy work-life balance. I was a great grad student: I published two papers in top specialist journals, presented at dozens of conferences, won awards, networked like hell, audited all kinds of classes, TAed every semester, applied for hundreds of jobs, etc. It didn't require me to give up on any hobbies or other fun stuff. And I'm not at all exceptional in that respect. Take the time to do your own thing. It'll help enormously with all the negative crap. Just don't let yourself get too distracted from your end goal!
As for making time for reading, I do most of mine on public transit, or for about an hour in bed at night. I often read during the day, too, but that's mostly down to how I feel in the moment. 
One word of advice: breaking your tasks down into smaller chunks and spreading them over time is way more effective than putting in whole days at a time. Read just one article a day, and by the end of a month that's a whole course's worth of reading; write an hour a day, and after a year you've got a draft of a dissertation, or after a few weeks, you've got a paper to send to conferences and journals; and so on.
The trick is to be consistent, and not to overload yourself with just one task. I try to write for about an hour a day (some days I get excited and it's more, and some days I lose the thread, but on the whole that's pretty much what it averages out to). I do that relatively early in the day, and then it doesn't matter what else I do that day; the pressure's off. I can take an hour or so to read a paper, too, and then that's two big things down. After that, the rest of the day is boring admin work, emails, course prep, whatever. And fun stuff.

FWIW, my anecdotal impression (from my acquaintances in history) is also that the job market there is better than in philosophy, though still terrible. Think along the lines of 100-200 applicants per job, vs. 300-600.
Also, as everyone else has said, avoid Chicago's cash cows.
It's totally possible to transition into philosophy from outside. It's not even all that hard, in the sense that loads of people do it. While a Master's degree in philosophy would certainly help, the most important thing is to make sure that your writing sample is up to snuff, and clearly philosophical. After that, work hard on your statement of interest, and on explaining why you want to move into philosophy. Clear and distinct (!) reasons are better than generalities, here: you need to make the case that you're serious about philosophy, and that it's the best disciplinary fit for you.
All that said, it's worth reiterating that although the history of philosophy job market is much better than the market for most other general areas, it varies a lot by historical subfield. And scholastic/medieval's job market is terribad. On the order of 1-2 jobs a year (almost always at Catholic institutions). And although there are lots more open/open jobs, they don't often seem to go to scholars working in that time period.

Now that we are past April 15th I suppose most of us know the outcome of this application season. I applied to 6 PhD programs, was rejected by 4 of them and waitlisted by 2, only to be informed yesterday that all slots have been filled. After months of waiting it was heartbreaking to be shut out in that way! But I guess there are many more of you out there who have been shut out for the season, so starting this thread for those who would like to share their story of being shut out.

Just accepted NIU - super excited!
Edit: wrong thread, sorry ? It's late and I've been doing my taxes...

Accepted my offer from GSU this week. (!!!)

Accepted my offer from GSU this week. (!!!)

Accepted my offer from GSU this week. (!!!)

Accepted my offer from GSU this week. (!!!)

I am surprised I found this thread buried on the second page given that we are now just a week and a half out from the 15th! I will be accepting my offer at the University of Minnesota for their program in Cultural Studies and Comparative Literature. 
I declined my lone philosophy acceptance (Marquette) and removed myself from the waitlists at Loyola and Michigan State, so hopefully this opens up some spots for people.

Accepted at Colorado, waitlisted at Michigan & North Carolina. Rejected by Rutgers, Arizona, UCSD & Georgetown. Applying from an unranked program. AOI - ethics, political philosophy, philosophy of law.
Very happy with these results. Even if I don't have any more luck, I love the Colorado program. I know that elite programs' waitlists probably don't move much, but I'm thrilled even by the possibility.

I've had pretty good luck this year: I'm in at USC and waitlisted at Rutgers. I suppose we'll see how things shake out come 15 April! 

Only got the one acceptance (and two waitlists), but luckily it was my top choice! I'm finishing up an MA at Boston College, and I'm thrilled to continue on to their PhD.

I've decided to go to Pitt. The only problem is that Pitt rejected me.

Hi All,
Thank you for the kind responses thus far. All very much appreciated. During my first go round in undergrad, I expected to be a lifer, myself. The job situation wasn't much better, and coming from a small school, I knew there was quite the hill to climb.  I was, and still am, highly aware that I may be relegated to exactly what I am doing for work at the moment. I was eager to embark, however. I never wanted a family of my own, and grew accustomed to the idea that most of my life would be spent trying to 'make it in Academia.' 
Teaching was a goal, and tenure would be great, but what I want is the access, networking, conferences and hopefully to write and collaborate with others to write. I'm running out of leg room on taking long shots with my life, and this happens to be one I simply have not had the opportunity to take. 

Just declined funding for an MA at SFU. Hope it helps someone!
By the way, is there anyone on here who is sitting on one of the nice packages from GSU? I'm apparently at the top of the waitlist for it, and it's the only thing keeping me from pulling the trigger now (freeing up other offers), so I'm curious as to what said person is thinking, if they're on here & willing to share.

Accepted at GSU's MA program! Was a late applicant.

Accepted at GSU's MA program! Was a late applicant.

Accepted at GSU's MA program! Was a late applicant.

Accepted at GSU's MA program! Was a late applicant.

Can claim BU for waitlist.