Apple and ATT have a 5 year contract, through 2012. Engadget managed to dig this up last week.
http://www.engadget.com/2010/05/10/c...xclusivity-de/
Barring some major loophole (ie. A completely different phone with different name), I don't put much stock in these rumors. We've only been hearing the same thing for at least 2 years now.