well there not as powerful but they don't have to be, pure balance and you get 4e. Once you balance it like that you lost me as a customer.
I don't like 4e, but I hardly think that it's the inevitable conclusion of going for balance.
In any case, I don't see how balance is going to be achieved whilst maintaining backwards compatibility with 3.5, although it seems to me that buffing the weaker classes is going to be more workable/popular than weakening the stronger ones (or rather, than weakening their spell-sourced ability).
The problem is that no one seems to want to buff the non-casters enough to bring them up to the level where the casters are. At which point the casters have to be brought down.
I don't want 4E, I want different and equally relevant. 4E is everyone plays the same - and that's boring.