The Legacy system is also due for an update, so BioWare is allowing players to focus on the portions of the game they like best to customize their alt character leveling.
In terms of gear, BioWare says it expects to see "more eccentric-looking groups tackling high-level operations" thanks to the adaptive mechanics. These changes allow players to wear their favorite social gear into combat while still enjoying the bonuses gained from their best combat gear.
Check out the full 1.3 patch notes at the official SWTOR website.
[Update: BioWare's James Ohlen has now posted a Welcome to GU 1.3 blog post to the official site.]