I'm guessing late October?
I'll go on record and say October 28.
You never can tell. Might be five months, might be eleven.
Probably be a 1.33 or 1.5GHz G4, hard drive bump, at most. As for "getting one this summer and hoping they'll be bumped", don't be silly. They JUST got revved less than a month ago. I don't think Apple is going to update them again in 3-4 months.
Get one now and be done with it.