Ok, so I'm no expert on OS X but from what I have read it seems 64 bit programs have been supported on 32 bit architecture since OS X 10.5 if the EFI is still 64 bit, which is common. So I don't think it would be a big deal to cease support for 32 bit OS X. Someone who knows more about it could probably chime in. But I would venture to guess that people who can afford to buy a mac probably don't still use an ancient one...
Reference: http://apple.stackexchange.com/questions...-8-leopard
Reference: http://apple.stackexchange.com/questions...-8-leopard