I suspect they'll try to get the Macbook Air down to a fanless design.
The chip in the current Air is rated at 15W. HP manages to fit the following 11.5W chip into a fanless laptop:
It doesn't have to have no fan at all, it can have a different kind of fan like a piezo-electric fan:
but it would be virtually silent under full load and never have to throttle performance due to temperature. This could mean better battery life too.
The MBP is designed more for performance but if they can drop from 50-90W down to 35-60W while maintaining the same performance, I actually think that would be an ok thing to do. In its current form, the MBP is roughly on par with the highest iMac and entry Mac Pro in CPU performance so it's hardly a slouch. Cutting down the heat and fan noise would be nice even just as a one-off and then boost performance the next time while maintaining the new lower TDP.
There should be another MBP release this year though. The Iris Pro likely unchanged but the 750M can move to an 850M.
I think quite a few people want to see a Retina Air this year and it's plausible but they still refreshed the old models this year so maybe it'll get pushed back to Broadwell so that they can go Retina and fanless at the same time.