I thought NASA had a satellite visiting every planet, but the website indicates nothing going to Neptune in the future. Voyager 2 is the only spacecraft to have visited.
New Horizons is on its way to Pluto, Cassini is at Saturn, and Juno is on its way to Jupiter. We have nothing in the pipeline for Uranus and Neptune, and until we ramp up our plutonium production, we can’t go. Solar power is barely viable at Jupiter.