Why on earth would Mass Effect show up? You'd think EA would have used it for their own severely lacking show if they wanted to show that.
For real, why would Microsoft give time to a slightly cleaned up Xbox 360 series in their next gen games show.
There are plenty of reasons. It's a very relevant franchise with a story on the Microsoft consoles. Moreover, we know that, by definition, this show won't be focused solely on next-gen games as there will be plenty of cross-gen. A ME trilogy could fit that. Although of course, it depends of what this trilogy will be. If it's a by the numbers approach than it makes no sense to show it now indeed. In fact, it makes no sense to make it in the first place.