...around Thanksgiving 2016 Cassini will be in an orbit which brings it as close as 3.63 Saturn radii from Saturn's center, between the orbits of Mimas and Enceladus. Then, on November 29, 2016 the spacecraft will use its penultimate Titan flyby to alter its orbit so that Saturn closest approach drops to 2.51 Saturn radii, just 10,000 kilometers beyond the narrow F ring, and not far from the outer edge of the main rings.
Cassini will execute 20 of these close "F-ring" orbits before setting up for a final close Titan flyby on April 22, 2017. This flyby will do something astonishing: it will perturb the orbit so that Saturn closest approach jumps, in a single leap, from just outside the main ring system into the narrow zone of safety between the inner edge of the innermost ring (the D ring) and the planet itself, just 3,800 kilometers above Saturn's cloud tops. Cassini will continue to thread this needle for 23 orbits (called, with some understatement, the "proximal" orbits) until a final distant nudge from Titan on September 11, 2017 delivers the death blow, altering the orbit just enough to drop Cassini into Saturn on September 15.
NASA / JPL-Caltech
Cassini's end-of-mission 'proximal' orbits
A schematic illustration of Cassini's final Saturn orbits in 2016 and 2017, according to the current XXM plan. The view is from directly above Saturn's north pole, with the main ring system shown in gray, and Cassini's path shown in black. The cluster of orbits crossing the lower part of the figure are the "F-ring" orbits which Cassini will follow from November 2016 to April 2017, and the upper cluster of orbits, passing between the rings and the planet, are the "proximal" orbits that will be followed from April 2017 until Saturn impact in September 2017.
The scientists on the Cassini team are incredibly excited about these two final phases, the F-ring orbits and the proximal orbits. They've told me that each of those two phases is like flying a whole new mission to a new location; each one will give new kinds of science akin to a whole small (Discovery-class) science mission, but with the full Cassini science payload. It's going to be totally awesome.