The SWTOR team over at BioWare just posted a small update regarding what to expect with game update 5.1. Most of this is already known, but there is some new info regarding a new cartel pack comming with the patch. Check it out:

Bolster your defenses with the galaxy’s newest gear, including never-before-seen armor, vehicles, weapons, and more! Lead a covert strike wearing the new Silent Warden Jedi robes, channel your inner fighter pilot with the Resourceful Engineer’s Armor, or roll into battle atop the Dread Behemoth tank. Check out the new pack in the in-game Cartel Market!

The other stuff about 5.1 were things we already know – 5 new uprisings, Master mode chapters.

Source: http://www.swtor.com/eternal-throne/updates