Such a great effort for an April fools...
I've always been a fan of the EX cast, shame there was no Skullomania in this!
It seems like Mihara from Arika tried to clarify what this is:
(This is a rather loose translation I got from someone else, so there may be something that got missed.)
"1. the exhibition is real
2. the game shown in the video is in fact playable
3. the fact that we hid that this was going to be the game played is the joke
Now we're concerned that no one is going to show up because too many people think this a fake event"
So apparently this is actually something they're working on? Or at least trying to convince someone to have them work on? Who knows.