With regard to the first paragraph, I'm not sure you're right. It is going to be easier to give a youngster playing time in a three man central midield rather than a two. I think he'd definitely get chances at Arsenal and perhaps City too.
Do you really see Mancini playing him ahead of what he has at CM? He has far too many option already and is in the market for De Rossi too. From what pogba showed when given first team games till now, he's not ready to start games for clubs like us city or arsenal as yet. Arsenal again have a very good set of CMs. But, with wenger there, he might sneak in a game or 2 but nothing significantly more substantial than what he gets with us. surely not worth a move as far as am concerned.
If its games he wants, clubs like City and arsenal shouldnt even be mentioned imo. If its a bigger paycheque, city is the place to be.