Honestly, whilst we can all see the inevitable fringe job that Scott Sinclair will have at Man City, I'd do the exact same thing. It's big money, after a good season with a small team who potentially have a limited shelf life in the league. He's going to have an opportunity to fight to play for the champions, and play in the champions league. If it goes tits up, then he'll have the opportunity to loan back out elsewhere (and probably still somewhere better than Swansea). Or he can pull an Adebayor, goto a smaller team, but continue to get paid by City.
It's the system that's fucked, I don't blame the player.