I don't know. I think lots of users are using good arguments. Both those who say it'll sell more and those who say it'll sell less. Truth is it's really hard to predict that, especially because of most important variable here, human behaviour, is very hard to predict. I mean just look ay several Pachter predicitions which fail hard, or the already infamous polygon MK8 prediciton. And those are supposedly profissionals...
Well anyway I withdraw my previous 13M prediction and throw a more safe 14M-15M bet, neither too conservative, nor too far fetched.
I still don't believe we'll see the same kind of behaviour we saw with previous generation because tablets still stole gamers from console gaming, even in EU/US (of course not near as much as in JP).