Why would you want MGS5 on Vita? How about its own stand alone installment like Portable Ops+/Peace Walker.
Leave "Metal Gear Solid" mainline series on consoles and spinoffs/enhanced ports/remakes on Portables.
It's MGSV(ita), not MGS5 if these rumors are true. At the end of the trailer a girl even says "Vee haz come two." That's enough proof for me that V is a letter not a number.
While I think this would be great on Vita and easily rendered on the hardware, I highly doubt it's exclusive. A Vita port however is very likely. No chance in hell this is Wii U exclusive. Sony and Microsoft would be extremely displeased about their logos advertizing a competitor's product.