My guess is that the iMacs won't be updated in September but rather sometime around March of next year. They may or may not be Intel based - your guess is as good as mine at this point.
As for more games coming to the Mac because of the Intel switch, nobody knows. Some may argue that there will be more games coming because the process to port the game will be easier and some may argue that it is still entirely up to the developer whether or not it's worth their resources to port to a platform with only 3% market share.
Sorry for being very indirect with my answers, but the answers to these questions are only known by Steve Jobs and the CEOs of certain game companies.
As always, if you are interested in buying an iMac, there is no reason to hesitate. The PPC platform will be supported for years to come and the current lineup of iMacs is very impressive.
Best wishes,
JOD8FY