A new Patch 4.3.2 is being deployed on test realms as we speak, this is a "minor bug fix patch." according to the official notes but we do not have more details for the moment.
World of Warcraft Optimization
The launcher now optimizes your game folder and tries to improve game performance/reduce the size of the install on your hard drive.
64 Bit Game Client
The 64 bit client might appear in this patch, the current test build is tagged as "test x86", which implies that a 64 bit version is available somewhere.