Shall I wait for GPU's to go down in price or for a new breed to come out?

You could ask this question anytime and there will always be newer and better cards being released.

Unless you know of a price cut that's gonna happen for a particular reason, then I would just go and buy the best one you can afford.

Yeah going midrange and upgrading once a yeah is probably more cost friendly than going all out on the most expensive card every couple of years. Depends if you somebody who's into saving money or just going all out for the latest and greatest.

4850 is probably the best card money to performance you can get at the moment, I know I'd get one if I could afford to!:D