While I'm still a bit peeved at how long it will be before Legion comes out, I'm still quite excited about the expansion, and the latest patch is filling it out in a few ways.
First off: Suramar, the highest-level zone is now open for testing. While the other four leveling zones will be available to do in any order, scaling to the level of the player, Suramar will be handled last. I don't know if that means it's a level-cap zone or if it will be for players level 108-110, but I'd guess the latter, as it would allow players to do two levels per zone.
The other nice bit of news is that there's another dungeon for testing: the Court of Stars, which I assume was the "Suramar City" dungeon. I'd actually despaired of seeing more 5-player dungeons being opened up, thinking that The Arcway (once called Suramar Catacombs) would be our only Suramar dungeon.
There also plenty of revisions to specs, talents, and other such things.
One curious thing is the addition of Order Hall armor sets. Not sure how those will be acquired, but they seem to be epic quality with set bonuses.
Also, it appears that there's a new souped-up PvP mount, which looks like it's the Goblin Trike. I'm curious about what the Alliance will get, given that the Worgen don't really have a unique mount (other than the "Mountain Horses" which old models there purely to avoid giving Horde players an advantage on mount collection achievements.)
There are still systems to implement, and the World Quests and Order Campaigns likely require a lot of implementation. Ultimately, though, there's already a release date. I can only hope that if they have things in good order months before the expansion releases that they'll be hard at work on post-launch patches.