During the XM, Cassini will:
- Orbit Saturn 60 more times, to study the rings and the planet in more detail.
- Fly by the biggest moon, Titan, 26 more times.
- Fly by Enceladus, the moon with active water geysers, seven more times. (One of these flybys may be as close as 25 km to the moon's surface.)
- Fly by Dione, Rhea and Helene one more time each.
And those are just the targeted flybys. There will be many more distant flybys of the so-called "icy" moons. (It's difficult to avoid them, considering that there are more than 60.)
More than 10 years after launch and almost four years after entering into orbit around Saturn, Cassini is a healthy and robust spacecraft. Three of its science instruments have minor ailments, but the impact on science-gathering is minimal. The spacecraft will have enough propellant left after the extended mission to potentially allow a third phase of operations. Data from the extended mission could lay the groundwork for possible new missions to Titan and Enceladus.
The TANDEM mission being considered by ESA will rely heavily on the results from the Cassini Tour & XM. (I love the Titan balloon. Very steampunk.)