Since nobody really brings this I guess I have to. (Please don't shoot)
While the X100 form factor is perfect, I'd like to see some minor overhaul with the lens ergonomics. I wouldn't actually mind it protruding half an inch more off the body if the lens gained a snap ring like the Olympus 17mm f/1.8 does. (Or the Fujinon 23/1.4 for that matter.) The beauty with the Olympus lens is that it accommodates two different modes of manual focus. When you snap the ring in manual mode, you get hard stops and distance scales. The throw is also very short and the focus range is slightly limited from its full range, truly excellent for street work with larger apertures. And not only that, you gain a "snap focus" type of feature: the lens instantly goes to the distance you last focused it to when you snap the ring.
But yeah, this is manual mode #1. The mode #2 is like we currently shoot MF with with the X100 series. In this second mode we have the usual stuff: possibility to use back button focusing whenever we feel like it, longer throw for precision work and the works.
I think they should keep the "X100" naming if they don't upgrade the lens and if they do, name it "X200".
And sure enough, weather sealing would be nice.