According to the patch highlights, patch 1.4.2's main focus will be on improving WAR's Tier 4 RvR combat. Power levels and power gaps are due for a tune up, and Mythic claims to have taken in a lot of feedback about the end game in order to make these changes.
As it's done in the past, Mythic is changing the scenario lineup for this new update, temporarily retiring some of these PvP instances while bringing others back online. The patch will also introduce a couple additional vanity pets, including the powder monkey and imp skeleton, which can be purchased via the EA Store. Some of these pets give you 5% additional gold when you loot corpses, making them very desirable indeed.
[Update: Mythic has posted the full 1.4.1 patch notes for your perusal!]