We've been told by Phil himself to look to previous X0 events to base on our expectations of what is to come out of X018.
Matt said next month (this month, November) would be very good for Xbox fans.
We know from Jez that he was told by an executive at Xbox that the 4 acquisitions at E3 were "only the beginning."
Both Gerstmann and guys at Waypoint have hinted at more acquisitions along the way.
I think it'll be reasonable to suspect an acquisition.
This reasonably expected acquisition may or may not be Obsidian.
I would think Klobrille posting the "Microsoft/Obsidian Entertainment" picture to be some indication but he may have been joking around.
So, to conclude, Microsoft is acquiring a studio and sharing that X018 is a reasonable expectation albeit not set in stone.
That is enough for me to be hyped up for X018.