Trailer also confirmed by Windows Central:
After confirming that I'd heard similar rumors (that may also include a Castlevania revival), I mentioned on my Xbox Two Podcast a couple of weeks ago that Metal Gear Solid 3 might be multiplatform, despite some previous assumptions that it would be PlayStation exclusive. I wasn't 100% sure at the time, hence no report. Since then, Insider Gaming came out with a report stating that it would indeed be multiplatform, and I have since also hard-confirmed that the rumors I'd heard were true.
Edit: he deleted the tweet