AT&T can lie and say that all they want. There is no reason in the world why Apple would not want to sell more phones. This is entirely AT&T's policy, not Apple's.
I totally agree with you, AT&T are the ones cock blocking us, and if we cant get past them to get the upgrade early how many people will wait for the 5, six weeks is not a lot of time to wait, but it then pushes you back for the next upgrade, because even if Apple follow this 18 month trend for the 5, we will still be short on the early upgrade.
I would hazard a guess that AT&T are hoping that we are rabid enough to pay the extra $250 to get the 4s early, and then again in a year when the 5 comes out.