I still doubt that MGSV will be cross-gen. But we'll see.
As for this being shown at the Microsoft conference, I find that highly unlikely. It would be foolish for Kojima to do so, when the series has been associated with the PlayStation brand for 15 years. No amount of Microsoft moneyhats would compensate alienating the huge majority of your fanbase. It's suicide. MGSV will either be at the Sony conference, or they will show it outside of the big two's presentations.