UPDATE 4/10/21: Smash Bros. boss Masahiro Sakurai will reveal the final character for Super Smash Bros. Ultimate tomorrow at 3pm UK time, in a presentation lasting 40 minutes.
Nintendo has also said we'll find out exactly when this last character will arrive, and invited fans to speculate on who it may be. The consensus seems to be expecting Sora from Kingdom Hearts. But we're still rooting for Birdo.
ORIGINAL STORY 23/9/21: The final character to join the bulging Super Smash Bros. Ultimate roster will be announced on 5th October, Nintendo said during tonight's Nintendo Direct.
Birdo, we're rooting for you.
That announcement will mark the final time a new fighter will be revealed for Smash Bros. Ultimate, which has received two season passes' worth of new additions at a steady rate since the game's original release back in December 2018.
Smash Bros. boss Masahiro Sakurai previously confirmed back in June this year that no further characters will be added, and there will not be a third season pass.
"Gathering all of these games, new and old, and compiling them into a single product is a task that has meant a lot to me," Sakurai said at the time. "Now that I think about it, it's been close to 10 years since Super Smash Bros. for Wii U and Nintendo 3DS was in development. I've been working on this for a long time. You could call it my life's work.
"But finally, the next DLC fighter will be the last one. There won't be any more after that."