I dont think we should sell him to City either, or any other rival for that matter. This season could/should be his best season for us and I truly feel we are very close to winning things.
If we win something he'll sign a new contract. If we sell him and buy a replacement who needs to bed in for a season we will likely win nothing again.
Keep this squad together plus make a couple of additions - Gervinho, Jenkinson, Ryo, another quality CB, and another quality CF and we will win things IMO