Just like Joker's video, it could introduce one or two extra modes.
Enjoy the videos and music that you love, upload original content and share it all with friends, family and the world on YouTube.
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Joker didn't have a true presentation video, they could "tease" the next character in the first few minutes then focus on whatever surprise they have left.
That's a theory of course and has no basis, but if they have extra content, they could easily do a ten-fifteen video without any issue.
My prayers go towards a Smash Run 2.0