Sure, they will wait in line for citizenship, but they'll be waiting in the USA. Not back in their country of origin, but paying a fine and back taxes, assuming they're dumb enough to claim any significant back taxes. It's like a tax amnesty, where you don't get thrown in jail if you promise to pay your back taxes and penalties, and everyone calls it just that, amnesty. And just wait - when all is said and done, the number that will come out of the shadows will be a multiple of the 12 million figure people have thrown around. It happened in '86.
Some people just can't be satisfied. I suppose you think you could do better huh?