Will Sora be a playable character in Super Smash Bros. Ultimate?

[Lef]

Cloud wasn't Nomura's decision to make, sure he helped on the game of Final fantasy 7, but he does not own it. Nintendo didn't even ask for Sora during Wii U / 3DS because he wasn't voted in.
Cloud got in because Nintendo held three voting polls, in Japan, the US and Europe. The US voted in Cloud, Japan voted in Corrine, and Europe voted in Bayonetta.
It was a rare event that Nintendo actually decided to put in characters that the fans wanted.
And it probably won't ever happen again.

I'm sorry, but this is absolutely not true. Cloud and Corrin are very much not ballot related characters. I don't know where you've seen that Cloud won in US and Corrin in Japan, but nothing like that was ever confirmed by nintendo so you're either assuming stuff or just making things up. Out of everything you said, only Bayonetta's win in Europe was confirmed by Sakurai.

 

[Rainclouds]

Either way, Sora is a highly requested character, so there is a chance he will make it in.
I mean Cloud got in. No one saw that coming.
Not sure why Cloud would get in and Sora be denied. I assume Cloud is more popular/well known at least. And perhaps he is easier to portray correctly. Perhaps Nomura didn't want Sora in the previous smash game as KH3 was in development, and the game added a lot more to Sora in terms of appearance/gameplay/etc. And he may have wanted to show Sora in the smash series as up-to-date, thus he may have decided to wait until after KH3, then he could possibly put him in the next smash game.

Anyway, there may be problems (like what has been stated), but there is still a chance.