mmsseeff

Oddly enough, I just sat in on a group meeting with a director of graduate studies who told interviewees to go contact any PIs they were interested in ASAP because it would be helpful to know how interested somebody really is when they sit down as a committee to finalize acceptances.
At this point, there's nothing to lose by contacting them. It might have been better to do it before, but you can't change that now so do what you can control.

I'm sure they're interested in your plans after graduation. Many students apply to PhD programs because they're motivated to become a professor and this is becoming increasingly competitive/difficult, so I'm sure they'll want to know more about why you want to get a PhD.