Haven't done some speculation in quite a while because of work, so I'm just gonna try to freshen my mind with some of the latest stuff. Could help with some people who stick to things that can't happen too
First off, Sakurai's latest Famitsu column outright deconfirms Blog Theory, imo. I mean, the theory is basically saying we'll get more fighters (7 or 8) in the next two months than we had in the
last two months (6, 5 being from the Smash Direct), which is quite literally the opposite of Sakurai's statement in his Famitsu column of wanting to slow down the pace of newcomer reveals.
Then, Music Theory is also in shambles right now. We got a Pokemon song this week, yet the most credible leakers such as Vergeben still insist on Incineroar being added in the playable roster. Given that the current speculation season had a lot of patterns and theories being outright broken, such as people dying on each trailer or Ridley being the only fan-pleasing newcomer, I could see Music Theory be another one of those things.
Right now, Box Theory is the only one that's still relevant. It fits Sakurai statement of wanting to slow down on reveals since it only implies we'd get two more, and it's overally pretty safe; one Echo and one newcomer. It also fits with the claims of Vergeben, our most credible leaker, so it's got a lot more going for it than the other theories ever did. Do I personally believe it? No. But it's really the only one of the theories people made out of the official website that still works.