This is Speculation right here, and it's my Ultimate Prediction. It might seem Crazy, but if it actually pays off, Just know someone out there predicted the Impossible
Smash Bros and Bayonetta 3 will Collaborate with each other in the Form of Shadow the Hedgehog coming to Both Games.
Bayonetta involves Time Travel heavily, so Shadow fits Very Well since Chaos Control is centered around it, (Maybe not Time Travel specfically unless we talking 06, but Time in general yes)
Sega made Shadow Playable in the 2017 game of Sonic Forces. Sega has been pushing Shadow as a Character Much more than the Early 2010's. Bayonetta was announced in 2017, and Platinum said they revealed the game too early, and It's very likely Development either Just Started or didn't even start yet, or the game was just Greenlit
The Same guy who made the Yakuza series (and also creative officer at Sega) said New Gameplay styles for Sonic were coming. Platinum tweeted a Picture with Sonic Shirt. Sonic Twitter account and Mike Pollock (eggman) tweeted "3" as a hint towards something. Sonic Adventure 3, Bayonetta 3, Sonic Rush 3, All three, two of those, maybe something else, it's something related to 3
Iizuka, Head of Sonic's Team, favorite character is Shadow
What I think will happen is that Bayonetta 3 might actually be coming in 2021, which FP2 is going into. Nintendo might have pushed for Shadow as a Character to perhaps Cross Promote. Shadow is a Requested character and is the 2nd Most Popular character in the Sonic Franchise, so even without Promotion he has Very Good Merits. That's a Win Win, as Shadow appeal to Casual Audience, Hardcore Smash Audience, Sonic Audience, and Nintendo, Platinum, and Sega's Interests. Also potentially Sakurai since he might like the more Edgier Characters (even though there's Much more to Shadow than Edginess)
Shadow in Bayontta 3 will push more units, or at least get more people interested in the game. Shadow in Smash would give Nintendo more money from DLC Purchases, and more attention towards Bayonetta 3. Sega will get Shadow in a game that's 95% likely to be good, and could be the steeping Stone towards Shadow Sequel, and then a Whole Franchise based around Shadow. I, and many will get their most Wanted Character in Smash, and Alsp My Prophecy of Shadow coming to Smash Ultimate will Come true