They will be working on designing, simulating, and building new missions to the outer planets. It's really important to have a roadmap for long-term exploration rather than doing one-shot missions, so you don't lose the expertise. The National Academy of Science works on this roadmap, and NASA generally follows it (see http://sites.nationalacademies.org/SSB/SSB_052297, in particular the Planetary Science survey from 2011).

It's a very exciting time for planetary science, especially regarding the "Ocean Worlds" (those moons of Jupiter, Saturn, and Neptune that have liquid water: https://www.jpl.nasa.gov/infographics/infographic.view.php?i...).

One of particular interest is Europa Clipper (https://www.jpl.nasa.gov/missions/europa-clipper/), although Europa is a moon of Jupiter.

I don't know what shape the team's careers will take, but this is anything but sudden for them. Planning for this started about a decade ago.

I remember years ago reading about all the options they were considering, including some really ambitious ones, like moving it to another gas giant over the course of decades. But costs would be high, failure a real possibility, and fuel very low. So we got the amazing last few months of images and science. And now comes the fiery end, with some final data and no chance to accidentally crash on Enceladus or Titan.