unlisted video so they probably didn't mean to show us
Releases August 7th.
Pre-purchase The Boomsday Project to receive a 50 card pack bundle, a random Golden Legendary card from The Boomsday Project, and the Mecha-Jaraxxus card back!
PLUS, you can also pre-purchase the new MEGA BUNDLE, which features an 80 card pack bundle, a random Golden Legendary card from The Boomsday Project, the Mecha-Jaraxxus card back, and a new Warlock Hero: MECHA-JARAXXUS!
Myra's Unstable Element pretty much done in WCDC several times i believe, cool feeling for the guys who "predicted" it :) Some other guys doing the Magnetic keyword right now in the Big Comp, just with a different name hehe. And ppl will finally get their "legendary (non-quest) spells". This expansion looks like it will bring the crazy out :)
Also if you check the description of the video it has the release date of August 7th and that there is a normal pre-purchase and a mega bundle pre-purchase which gives you 30 more packs and the new warlock hero mecha-jaraxxus. So warlock getting a new hero confirmed already.