To clear it up, Sakurai didn't say Home Run Contest was the "last mode", he said there was no plans at the time for doing modes beyond it. Plans can change. I think we're getting no more, mind you. But he said the same thing about the Pass, so. I'd wait to see what happens. It's left open vague just enough in case he is able to do something not planned earlier, while a case where he doesn't need to change the wording cause it's clear to not expect that particular thing as is. Good strategy, imo.
To note, I think we're outright getting a reveal tomorrow. Them not mentioning it is just more of a way to get people hyped up, since they can go in unexpected. It could be a smash direct announcement, but that's highly unlikely, imo(more likely than zero news on any kind of Character DLC at all, mind you) Nintendo being vague causes more speculation, and they seem to think it helps hype. That's not that true, but they did pull it off with ARMS(also to help get more sales), so they do have it on their mind that being vague "works".
...Yes, vague can both be good and bad in context. Heh.