Well, no invite for me yet. But there's good news on the Beta front! Two of the four leveling zones are now up for testing. It also looks like many, if not all of the artifact acquisition quests are also open, which is pretty cool.
And the best thing: it now runs on Macs!
I'm sure we'll get a ton of new information and plot spoilers coming soon.
As we know, there is no official "first zone" in the Broken Isles. You'll be able to do Highmountain, Stormheim, Val'sharah and Azsuna in any order. Suramar will be the last zone (not sure if it will be like 108-110 or if it will be pure level-cap content like Vale of Eternal Blossoms.)
But this is definitely a step in the right direction. Assuming we keep the usual pace of betas past, we could easily see Legion drop in the first half of 2016.