The IBM processors used in the current line max out at 2.5 ghz by IBM's own design spec, so I'm not expecting anything more than that. Apple has taken that chip set design as far as it can go by using the highest speed IBM makes and multiplying it by 4 (the quad).
Rather my thought was that since there is still about six months (a hell of a long time) to go before even the first desktop Intels, and a whole year until a Photoshop UB (not to mention printer and scanner drivers, monitor calibration software, 3rd party plugins, raw converters), I'm hoping they'll "tweak" with better video cards, larger HD, or maybe use the highest 2.5 speed in the dual core model without any price leap. I guess we'll have to wait and see, but I agree any tweak won't be earth shattering, just perhaps giving us a tad more for the money than they do presently. It's more a question of better configurations using current technology at a given pricepoint, rather than any breakthroughs.