I want this to be real so ****ing badly.
But I'm not really buying it. Something about every picture just rubs me the wrong way. I won't start with crazy investigations and artwork comparisons (doing that just leads to "Shulk is a little mac edit, guys!") but I don't see any reason to believe in this just going by those pictures. We've seen some good fakes before, this can perfectly just be one of them.
Not to mention, I already told myself that I'm not expecting any DLC characters other than Mewtwo, especially not at the same time.
So yeah, I'm calling fake for now. And I don't think anything short of official words or a video will convince me otherwise.