Built in eSATA would be cool, but an ExpressCard/34 should take care of that. If Apple would just make some decent ExpressCards for us (eSata, iPod Dock connector, GPS, EVDO, EDGE, GSM/3G etc), that would be ideal. 3rd party is fine, but Apple should really take the time to kick start the innovation. Its been a year and still these cards seem more rare than the PC Cards they are meant to replace.
Along that line of thought, I'd like to see the ExpressCard reach into the MacBook line so we have a chance of getting an integrated cell modem or FW800.
I'm okay with the MacBook not having real graphics, but why should a pro use have to make do with a 15" screen when they really want something like 10-12". Either Apple will bump up a top of the like 13" MB to Pro levels, or it will go for a smaller tablet form factor for the MBs. Imagine the MBs all having touch screens and the MBPs all having standard keyboards. Then we could get a 12" MBP and not cannibalize the 13" MBs' sales.
I think it is pretty clear that there is a touch screen Mac coming and its going to be a portable device. Based on the demos I've seen online, all the interaction so far seems very consumer oriented, so a MacBook upgrade would make sense. When the Pro apps start accepting multiple user inputs, then maybe the MBP will upgrade.