Look, I love Rayman and I'd say he's my most wanted platformer character with Banjo and Kazooie in the game.
I just don't see him making it. Others have pretty much covered my points already, but being obscure in Japan is a hard hit against him, especially for what might be an E3 reveal and then literally the DLC pack that Ultimate is supposed to end on.
Also, the people dismissing the Brawlhalla thing are skipping over the context of his presence in there. It's not the same as Terry in EX Layer or Snake and Simon being in that weird Japan-only Konami brawler that came out even before Brawl.
Rayman was added to Brawlhalla on November 6th, 2018... about a week
after he was revealed as a Spirit in the November 1st Direct (he was originally announced on the 2nd, a day after, too). Which means that, if Ubisoft tried to negotiate for him in Smash before then (like they did by sending the trophy model back in 4), they were denied some time before that date.
And Brawlhalla isn't just a random crossover game - its creator, Blue Mammoth,
had joined Ubisoft as a subsidiary that same year.
So yes, it very much felt like Ubi had failed in their negotiations (which likely extended up to Volume 1 DLC) and went "**** it, we have a studio with a decently-sized platform fighter, let's put him in there".
Now, obviously, all of this means **** for Volume 2... but if Ray hasn't made it by now, I doubt he'll be among our last reveals.
(Sincerely, a Rayman fan since Rayman 2)