Well, I am sure that whatever the Dual-classing does, it will not change the number of feats, powers etc in a big way. With the current multi-classing you can get one more daily or encounter power, but the only other way to get more powers is to get the right magic items.
And that, in my way of thinking, is what keeps the current multi-classing balanced. You can change powers, by spending feats, and theoretically get new abilities, but at a cost of feats. On the plus side, some of the power you choose can close gaping holes in your character or give you very useful power, otherwise why take them?