NASA had announced recently it was considering repurposing the healthy spacecraft to explore the Sun's effects on the outer solar system. This was a controversial movie that met with resistance among the planetary science community.
The New Horizons team is searching for another flyby target in the Kuiper Belt that it could redirect the spacecraft towards.
New Horizons has enough nuclear fuel left onboard until 2040. I think it will be a long time before humans ever get another mission out to where New Horizons has been and is exploring. It will be able to a lot of science in a number of ways.
Sky Guy in VA