Star Wars: The Old Republic is going offline for about four hours tomorrow, to lay the groundwork for the 1.3 "Allies" update. The maintenance downtime is scheduled to last from 12 AM PDT until 4 AM PDT, so chances are it won't impact you unless you play into the wee hours. After that point, you'll be able to restart the game launcher to update to 1.3.
BioWare provided the maintenance notice on Friday. As previously reported, the update adds a dungeon group finder, a new augmentation system, a socially adaptive skill system, and a revamped tutorial. It also adds new perks to expand on a previous update's Legacy system.
If you're curious to try out the new update, but don't own SWTOR, you won't have to wait long. The game is going free-to-play up to level 15 in July. It seems like a half-step towards a full F2P model, as many MMOs have been adopting lately, and BioWare acknowledges the possibility.