I'm thinking that myself. I have the 16 GB version pre-ordered but if and when the 32 GB version becomes ready for pre-ordering, I'll call that number on the AT&T business card I received and have him switch it out.
I just don't want to run out of room for apps and other various data as well. Plus, it's only $50 more so who cares. I can make that up easily with selling two phones that I have.
I figure that I'll get anywhere from $175 to $200 for each of the phones that I have.