Starwars.com has posted their episode guide for "Carnage of Krell" (S4 Ep. 10), and the synopsis informs us that we're not necessarily getting a happy ending in the conclusion to the Umbaran story arc.
"With two of his men facing execution for disobeying orders, Captain Rex must confront his overly aggressive commander, General Krell. Risking charges of mutiny, Rex must make a dark choice as the true face of the enemy emerges."
Click here for images, a trailer and the opening tag line.