Well first of all, it won't be an orange booth, it will be an 'AT&T blue' booth.
But seriously, we all know Apple would never agree to that. Apple will simply have certain employees from each store pass whatever training course a standard AT&T store worker has to pass, and they will be given access to the software, connections needed to set up the iPhone in the store. You will buy the iPhone, and then walk over to the 'Activation Bar' or whatever they'll call it, and there will be 1 or 2 people there to instantly assist and activate your new phone with contract.
I'm making a guess here, but the reason it takes so long in regular cellphone stores is because the process is different for every phone? Possibly, the process could be streamlined because there will only be one phone and the activation will be the same everytime? I can see maybe just filling out a quick sheet of your information, address and whatever.. and then the rep gives you the phone. While they engage in the activation process, they hand you the phone and you can play around with it. Obviously the time it took to activate the phone would no longer be an issue, because you'd have the pure joy in your hands to play with. You wouldn't care if it took 2 days.. (and probably wouldn't notice either 😉 ).
Anyways, my point is that Apple will find a way to make this process quick and easy.