Hi Zues, I am contemplating doing the same thing (applying to a department with a better fit when I finish my MS next year), and while I can not give an informed opinion regarding your situation I am curious how you handled applying to other schools without offending those in your current program. Any advice would be appreciated.
For what it is worth I would say leaving and coming back is the least favorable course, it will take a lot of explaining and may still not work out in your favor.