It seems that what could not be avoided just happened and Apple has cancelled the possibility of unlocking any iPhone irrespective of the service provider network. This cancellation was only a rumour a couple of days ago, yet it is now official.
Nobody can perform SIM unlocking procedures for AT&T, for example, or for any other networks that allowed unlocking a week ago. This is a normal thing to occur since tens of thousands of iPhone owners desperately rushed to have their terminal unlock as soon as possible. Eventually, it was proven that all this happened in an unofficial manner, therefore without Apple being aware of it.
At this point, the only problem seems to be the locking of the terminals, which Apple could do if they wanted to. I personally do not think that Apple will do this. But if they will, then those who have already unlocked their phones and kept the unlock ticket, can save the unlock ticket and use it in the future without any problem. If you choose to lock you iPhone via iTunes, then your unlock procedures become invalid and the money you paid for it is wasted. The persons whose terminals are still locked, but they have paid for the unlocking will probably get their money back.
Be aware, nobody can unlock devices for AT&T or other networks that could not be unlocked last week. Do not trust those who pretend they can, it is a scam!