I'm kind of sweet on getting a 13" these days, as a compliment to my desktop, so:
13"
higher resolution. Actual usable resolution, not just double pixels HDPI and the same limited screen real estate. I'd like to see 1080, or 1050 in the 13", and doubling that to retina-style would be fine and dandy.
Quad. I think it's doable, and it would be oh so tasty in a package of that size.
Dedicated GPU. Might be getting a little liberal now with my requests, but why not! To be honest, the 4000 might fit the bill for most of the things I'll do on that machine. As long as my flash videos aren't looking like a powerpoint if I decide to hook it up to a TBD, I'll be happy.
Upgradeable memory and hd.
That's pretty much all I need. I'd be happy with an updated chassis that loses the ODD and fw, and has 2 usb3s and 2 usb2s and an sd reader. Having said that, I don't care all that much. I'd just like it to be a bit more useable with more screen real estate, and a couple more physical cores. These machines really are a marvel presently and I'm sure they'll raise the bar even higher this go around.
I hope we start seeing the flurry of rumors this week, so we don't have to keep regurgitating our ideas in these silly threads to keep ourselves entertained and stimulated 😀