I've got a question for you guys.

When you cancel IFR, doesn't ATC say something like "... radar services terminated, squawk VFR"? If you're in the middle of class-B when you cancel they aren't going to say that.

It seems to me in this situation the ball is in ATC's court - they have to give you some instructions. Either squawk (bla bla bla) and maintain your current heading, or get your little 172 out.

In the last case, pretty much all you'd have to do is descend a little bit and you're good to go.