So here's what I'm thinking. I am looking at this without bias, or at least with as little bias as possible.
Tomorrow the video will be around 3 minutes. It will not be a full presentation, and the comments from Sakurai aren't mentioned in the Japanese presentation. I have heard different interpretations on this, but I'm not sure exactly what to think.
On one hand, it's been suggested that if it's a western only thing, that it would be Sakurai explaining the character because they're obscure to the west. However, with characters like Byleth, Terry Bogard, and even Dragon Quest, Sakurai has spent a sizeable chunk of time talking about each series. If the character were Reimu, or something, I doubt the talk would be 30 seconds. You'd need significant time to talk about a relatively unknown pick.
On the other, and in my opinion a more likely scenario, is a character that, for now, doesn't need a longer introduction. It's somebody that many could recognize and "get" off the bat. I'm not throwing chips into any particular table here, but games that come to mind are...Pokemon, Mario, Zelda, Devil May Cry (Dante is relatively well known, fyi), Crash Bandicoot, etc. This is why the form of "What is X?" wouldn't apply...it's not a long enough presentation to bother with that, so there's no ridiculous, "What is Pokemon/Mario/The Legend of Zelda".
In terms of what Sakurai will say, I really don't know. My guess is something about development, but that would probably also be said to the Japanese viewers. On the flip side of that, despite the different titles of the videos, it seems possible that, if the same length, it's the same video with different labeling for consistency.
I'm not really sure what I think, but I don't necessarily buy that it's an obscure character who needs explanation.
What makes this whole thing interesting however is that with every character is a content update, with potentially new features, Mii Costumes, etc. There's a lot of content we're losing here, which does seem to indicate that there will be another presentation at another date with that complete description.