Here's my hot take based on the previous comment:
I honestly would have very little interest in an Ultimate Deluxe. I've been playing Ultimate for almost 7 years, but I acknowledge that it's probably what makes the most sense to do. After the success of Mario Kart 8 Deluxe, they probably realize an Ultimate Deluxe would sell as well as a Smash 6, while still being much, much cheaper to make. A Smash 6 would be a harder sell than an Ultimate Deluxe because of the cuts. I personally don't mind cuts, but most people do, and they're not going to buy a Smash game that cuts characters they like. It's just how it is. I don't think it will be anywhere as bad as Dexit, obviously, but a lot of people will be upset. I think Dexit was a special case.
"Street Fighter 6 was well received despite the massive cuts." Yes, but the SF fanbase is not the Smash fanbase. SF players have different expectations than Smash players. I see people bringing this up, but I just think the comparison doesn't really work.
"Mario Kart 9 is happening despite the potential massive track cuts from MK8D!" This is also a point I've seen previously brought up, and honestly, I did too. But honestly, I don't think it's quite the same. I think it's easier to sell a Mario Kart game with a different track roster from the previous game than a Smash game with like 10 cuts or more, especially if those cuts include fan-favorite characters like Sora, Hero, Sephiroth, Palutena, or/and Joker. (Not saying they're likely to get cut, just hypothetical.)
I also feel like it's harder to think of new modes or mechanics to add, which might also make it harder to justify Smash 6.
So basically, I personally want a Smash 6, but I expect an Ultimate Deluxe. The latter just seems like it would be more successful.
I will probably buy a PS5 instead of a Switch 2 for Christmas (assuming Switch 2 is 2025 and Ultimate Deluxe gets announced this year) if we get an Ultimate Deluxe, tbh. I have a backlog for PS5 to play, and I kinda want to try 2XKO, so I'd have the perfect excuse at least. I can wait to play Mario Kart 9 and Gen 10 for 2027 or so.