I have been wanting to purchase an iPhone for awhile now, but there are a few features that are lacking, notably, 3g and gps. with the announcement yesterday from att's ceo that 3g will come out this year i can finally see that happening. rather then wait till the end of 2008 however, ive been thinking of purchasing a gen 1 iPhone and then selling it when the new one comes out.
Is that is a feasible plan? will a pre owned iPhone be sellable? I understand that you have to activate new iPhones through Itunes and sign a new contract with ATT, will a buyer of a used one be able to just pop in his sim card if he has an ATT account?

Also, if I buy a replacement iPhone, would I be forced to create a new ATT account through iTunes (thereby being on the hook for 2 ATT contracts) or will i have to extend my contract for another 2 years? I dont know anyone who actually has the phone so I dont know how the process works. any help would be appreciated so I can ditch my samsung, thanks!

edit: just realized i posted this in the wrong forum, sorry, please disregard or move to general.