Telescope capabilities (James Nicoll and others?)

Given what we expect to either orbit or build in the next 20-30 years, what would be the resolution of features we could see (or could we see at all) an object ~50km in size at various distances -- say a little outside of Pluto's orbit, inside of Uranus', inside of Saturn, and at Jupiter orbit. Assume there's sufficient interest that any instrument available could be commandeered to look at it. Additionally, (1) would there be any improvement in this capability possible over a few months' time (by presumably sending up new instruments -- I would assume not but I've been surprised before), and (2) what else could other instruments (radar, spectroscope, etc.) tell us about the object at these distant ranges?