XCOM new DLC?

Purely speculating, and you may be correct, but;
The iOS version is just a straight optimised port, according to the description the teaser project was described as their new 'big project'. Highly unlikely they've invested all their man hours making an already existing game work on another platform. What is more, your video shows actual footage of the iOS version being played on an iPad, and appears to be from the same event the other video was shown at...why would they show that, and then make an incredibly vague teaser trailer for it?

That makes it seem more likely the teaser is for something new, presumably DLC and not simply for the iOS version.

I thought it's a separated project?

No

it's 21st century dude, expansion no longer exists anymore

however It will be totally awesome if it actually is an expansion, but I doubt it :)