I think we've all lost our minds. Really, though, I think you're half right. This is Apple: they wouldn't cover over an icon, or slap up a sticky icon patch over an existing poster. But, this is Apple, they would pay for whole new posters right after having all those old ones done.
I actually have to agree with you, there.
There's no way Apple would just throw a "sticker" up on a poster. They're far too "classy" for that.
But really, in the scheme of things, what's a few four color posters for each Apple store cost them? Probably a fraction of a fraction of their iPhone marketing budget, regardless of how nice and high quality they are.
Still, count me among those not expecting new apps...