I was in the same boat as you... two years ago. We waited... my daughter went off to college with her 4 year old iBook. The new MBP's came out in late October... now half way through college her MBP is still good enough and will carry her through the next 2 years.
Apple will update both the MBP and the MacBooks sometime before Christmas... it's my understanding that Intel has slipped the new chipset a month or two... just tell your son to hang on... when the new machine comes out you will get him one and he will be glad he waited that extra time.
That's a funny coincidence -- my older one is heading off to college in Sept (my boy has her old iBook) -- she's his polar opposite in that she hates to upgrade, so she's holding onto her Rev A Macbook until the new version, so she may not get her "college" computer until December....
JT