We can do, particularly as we progress, but that's the whole point of the new stadium, the wage structure won't be as strict once we have the income to match.
That second bit is a bit of a myth - we sell no more players than anyone. United, Arsenal, Liverpool etc. all sold key players in recent times. We haven't had to sell a key player to any club in England since Berbatov - it just doesn't happen anymore. If we do need to sell for huge money we will sell abroad.
Thankfully I don't see that really being an issue for the time being, certainly not this summer, and in all likelihood not the year after either. The only one we may see as expendable if he wants to go is Walker, because £50 million for a Right back is insane.