I have fully embraced Micro Four Thirds. I have four lenses, along with one standard Four Thirds, and two bodies. It has quickly, albeit not completely, replaced my APS-C camera. This is what I, as an enthusiast consumer with a fair amount of disposable income, would like to see in upcoming products.
As far as lenses go, things are already looking incredible. Zeiss and Sigma both just signed on to the format, and they're likely to simply adapt their larger lenses at first. This means large, but high quality. I have all of the cheap lenses that I could want, and super-large, pro lenses aren't very appealing, so what I want are mid-priced ($1000), mid-sized prime lenses like Panasonic's Four Thirds 25mm Leica lens. These aren't so big as to be silly, but are large enough to eliminate many of the shortcomings of pancake style lenses. I figure that Olympus will be releasing versions of their pro Four Thirds lenses some time in the future, so if I do want pro, it'll likely be there, and the 12-60mm lens they produce is a good example of what I'm looking for in general. Also, Olympus' 50-200mm zoom lens is a good example of the upper-limit of size that I, and I think most m4/3's buyers, would consider.
A next generation sensor is a sure thing, since that's just the way the market evolves. Instead, I'd be very interested in different types of sensors. Be it sizes similar to Panasonic's multi-aspect sensor in the GH1/2, or maybe one from Kodak or Foveon. With no legacy hardware or market, the sky is the limit. I do not want to see conservative movements. Canon and Nikon give us enough of that, already.
I differ from most other bloggers in that I don't care if they make a weather-sealed body. None of the lenses are weather-sealed, and aiming m4/3's at such a pro market seems unlikely to meet with success. Pros spending that kind of bread aren't going to be willing to sacrifice the power of larger sensors in the quest for lighter bodies. This always seemed like the obvious reason that Four Thirds never took off in that market, even with Olympus' excellent pro lenses.
What I would like to see is a compact body with pro-level features, specifically Compact Flash. A jog dial would be nice, as well. Because once you've had a jog dial on the back of a camera, you never go back. I don't give a crap about an articulating screen, give me that dial! In fact, the Olympus E-5 would have been great if they hadn't left out a jog dial and priced the thing clear out of the solar system. Or, even better, the upcoming Fuji X100. Remove the lens from that camera and you'd be sitting at about $1000, and it's got everything I could want save for Compact Flash.
I would say that I would like to see a direct competitor to the X100, as in a point-and-shoot with a 4/3's sensor, but after holding the Panasonic GF2, I have changed my mind. When combined with the 20mm or 25mm pancake, that camera is so comically small in the hands that it basically counts as a compact.