What new tank? That's a Heph between the Kit Fox and the Adder.
Visible we have, from left to right: Nova Cat (shoulder and right arm visible beyond the Shadowcat's shin), Shadowcat (foreground left), Mad Dog, Kit Fox, Hephaestus, Adder, and Mad Cat Mk. II.
The shadows of otherwise-unseen assets look like the Xerxes (in front of the Shadowcat's foot) and a possible Blood Asp (above and behind the cameraman). On rightmost shadow, the arm curves away at the wrong angle to be a Thor as someone upthread speculated. The gun profile visible on its right shoulder matches the profile of the Blood Asp (which we already know is functional in the alpha builds anyway), and the difference between the two shoulder-mounts looks more like a changing angle on that rock than different pods on the 'mech. The squarish shape between the two gun pods isn't a head -it's the air intake-looking thing on the top of the Blood Asp.
And really, guys; forget the 'mechs. There's no surprises here. That map, on the other hand... damn. I retract my previous statements about Swift Winds and the inviability of hovercraft. That terrain (those mountains looks familiar... Utah, maybe? Somewhere western US.) was made for a fast-moving, low-profile scout. Speed is life over ground like that.
[edit: scratch that, more likely a Sulla]
