Let me point something out here which may or may not be of use in the grand scheme of this discussion...
There are three hypothetical situations where a "leaked" screenshot could've originated:
1. Screencap software on the computer of a developer working on SSB4, where it would just as easily be possible to cap video. This is unlikely, as an actual screencap would readily reveal the fact that someone on the dev team is leaking info.
2. An off-screen picture taken by someone, in which case it would be just as easy (if not easier) to capture video, as I explained earlier.
3. Someone making fake pictures to troll us because pictures are easier to fake than video.
If anyone can name a situation in which a genuine leaked screenshot or video could be generated other than those I've listed, I'm open to suggestions, but I believe this covers it.
Thus, I'm extremely skeptical of any leaked screenshot because the obvious question every leaked screenshot raises is simply "Why did you not take a video?"
This isn't 2001. Bandwidth is plentiful. People can upload video to facebook (or 2chan) directly from their cellphones. There's really no excuse for not getting video instead of screenshots, unless the goal is to troll us with fakes.