I say fake, if for no other reason than that XenoMech sounds really fake. I mean let's be honest, it sounds really bad. Not a good title, even if it is real.
And does Nintendo really give a master list of all their E3 secrets to people to take pictures of? It's not even in a folder, it was just copy paper stapled in the corner. Seems unlikely Nintendo all of companies would be that lackadaisical with their most important secrets. I am guessing all of their E3 reps they use for the show are shown things in a secure location to familiarize themselves with games, and not just handed a stack of paper with the keys to the kingdom.
Also, Sunshine HD is a day-one purchase for me, but Wave Race? C'mon... that's a really odd choice. Of all the GameCube remakes to consider, why do Wave Race to go along with Mario? Why wouldn't you do Metroid Prime 1 or Paper Mario TTD?
Wave Race? lol...