I think that once the lens range is filled out we will see variants of existing lenses at the same focal length and Mk.II versions of existing favourites.
Gazing into my crystal ball I therefore predict (store this away and you can beat me over the head with it when it doesn't happen...):
1. A fisheye, 6-8mm
2. A fast (f2.8-ish) single focal-length super tele in the 500-600mm range
3. A 27mm f2.0
4. A Mk. II 18mm f2.0, 35mm f1.4, 18-55mm, 60mm, all with faster focus and weatherproofing
Bear in mind that the next generation sensor is likely to be 24mp or greater. Some of the older glass will struggle to produce stellar results with that.