Chances are - it's a screenshot of a development prototype of the app. It may have had the working name of "4D" and been changed to 6D for release.
Either way, it requires a WiFi connection (which only the 6D has as a built-in feature) - so I think that's the situation.
I will take your theory and put on my tinfoil hat...
/conspiracy mode on
What if this was all just a big ruse to get people talking about the app? I mean its not hard to replace details such as the number in a video, just takes a few mins in after effects.
Or better still the company that made the app purposely put the name 4D in there for another camera then took the video knowing full well that it would raise interest on the net and get people talking about their app.
Because lets face it, before this mystery screen grab/video how many people knew about this app? and how many MORE know about it now?
/tinfoil hat mode off
But all seriousness i don't know why the new camera couldn't be a 2D. especially if they were to double their current highest MP number. So suddenly we have the new canon 2D 2x the MP* of the Canon 5Dmk3 (*=48MP) .
Or something corny like that.