the national academy of science's planetary decadal science survey committee recommended that we send a battlestar to uranus, so we'll learn a lot more about that (and its moons!) in ~25 years. there's likely to be a triton flyby mission around the same time as well, probably trident.

the chinese have mooted a neptune orbiter, but that wouldn't be launched until 2040ish, and even with the proposed nuclear-electric propulsion, wouldn't get there until 2053-56, depending on how big a push they can give it.