That's true, but they could tie it to the anniversary. If Sakurai had planned to have a mario character from the start then i can see Nintendo wanting to ask to conjoin the inclusion along with the celebration of Mario's anniversary. I can definitely see this being the case as i'm sure they had plans for mario before the pandemic hit hard.Thing is, while Nintendo's making a big deal of Mario's 35th anniversary, Smash tends not to choose characters for celebratory reasons. Not only that, we've never had a newcomer reveal before in a series-specific Direct (other than Smash ones, obviously). If there is a Mario character set to happen soon (my instincts, as little as they matter, keep telling me Geno might be next), it'd be for reasons unrelated to the anniversary (like being a highly requested character that'd fit what would've been an E3 reveal like Banjo and Ridley the previous years).
Try not to get caught up in all the talk of pomp and circumstance. Lot of speculation still treats characters and their announcements like a means to an end of representing or commemorating something, but Sakurai has said the characters are an end themselves.
I'm not in the mindset that smash characters would strictly be added to help promote stuff like anniversaries, but the opportunity is there and would be foolish not to take some advantage of. They did take advantage of the release of the definitive version of DQ 11 and pretty much promoted that game alongside Hero's reveal, so it's not too far-fetched for them to use the opportunity somehow. Pokemon could be the same next year.
But until we get the next character we won't know for certain. I'm still in the belief that fighter #7 is a 3rd party till otherwise.