Waluigi:
Chance: 40%
I think if any assist trophy looks like a front runner in regards to being upgraded, it's Waluigi. Like, seriously, when you have videos like
this one with millions of views, and when you have Reggie talking about how the outrage over Waluigi's AT appearance was big enough for Nintendo to notice, it becomes quite clear that Waluigi has generated a lot of noise despite being not playable. The only other character to generate similair noise was Ridley back in Smash 4. I believe we'll get a fan favorite character in pass 2, and I don't see why Waluigi shouldn't be counted among the possible candidates for that role. He's popular, he's very requested, and Nintendo acknowledges his demand.
People believe assist trophies are impossible to upgrade as DLC because of whatever reasons. Even though many fighting games have already done the NPC promotion before, people seem to think Smash might be the exception and every single character already represented in Smash that isn't a fighter has zero chance to be promoted. It's an odd idea but it's a fairly popular one among the fandom.
The main argument against AT's not being able to be promoted is "it hasn't happened yet", which doesn't seem concrete to me since you could say the same thing to a lot of characters that "haven't happened yet" before they got in. NPCs not being able to be promoted to be a playable character is a misconception the fandom had even though neither Sakurai or Nintendo said promotions are not happening of any kind.
It is likely? No.
Is it impossible? Hell no.
I believe Waluigi has a chance of being playable, and if it ever happens then that's another fan rule we can throw away.
Want: 100%
My most wanted character for over ten years and still counting. I think Waluigi fits Smash really well and he's someone who arguably should've been playable already. If his moveset is anything close to the other three Bros then I'll have fun with him for sure.
Isaac
Chance: 20%
There is one main problem I see with Isaac's chances, is a new game actually coming out? People theorize that there could be a new game coming out, what with the trademark and Camelot being silent for 2 years. If a new game is coming out then this score will go much higher, but since we're talking about a game that we don't even know is in production, it makes ranking this character quite difficult. I will say that Golden Sun doesn't have any playable characters, so in a way that's one point in it's favor.
The trademark could mean nothing in the end, or it could mean a new game. At the moment I see Isaac as a possibility, albeit an unlikely one. Isaac's fate for Smash ultimately depends on if a new Golden Sun is coming out or not. We'll just have to wait and see.
Want: 70%
Originally I wasn't that interested in the character even though I played the original Golden Sun years ago. But over time I have come to appreciate the potential that Isaac could bring with him, what with him being a geomancer. I do wish to come back to Golden Sun and play it's sequel, but I don't think I'll ever have enough time for that in the near future since my backlog is already so clogged up.
Nomination: Kratos x5
Prediction:
Bandanda Dee 29.7%
Dixie Kong 22.7%