Money doesn't always talk, especially when you have no need to sell. Every top club has some "unsellable" players (within reason... you aren't going to turn down £150million for Aguero but no one is going to bid £150million for Aguero), members of the backbone who are so important that selling them would do more damage than good. For us that backbone is Hart, Kompany, Yaya, Silva, Aguero.
Selling Mario (done), Dzeko (likely), and the aging Tevez (possibly) would allow us to buy one of the best strikers in the world to partner Aguero, who hasn't even entered his prime yet and is very happy here no matter how many times the newspapers regurgitate ancient quotes from him.
Tevez will significantly deteriorate as a footballer soon, he isn't a Drogba style striker who will be great when he's 33. He is already far easier to cope with than he was a couple of seasons back. So the OPs question is a very easy one to answer really.