I'm gonna go with what
Fatmanonice
said not too long ago and think that the Fighter Pass is a celebration of gaming culture, while the post-FP DLC is like the fans celebrating Christmas with Sakurai. I knew as soon as Hero and Banjo were announced as DLC #2&3 that Geno wouldn't be neither 4 nor 5, so it was very relieving that they confirmed more fighters after the pass.
Me, personally, I think that Lloyd Irving is the most likely candidate to be #5. It wouldn't be too crazy to announce him at the VGA as Tales of Symphonia was the first game in the franchise that people in America and Europe noticed and really loved, the reason why (most) of the other games were brought from Japan. And this way, we have in the FP 5 big characters from 5 big franchises.
The post-FP has no rules though, so I think Sakurai is going to give us a lot of things that we've been asking for years, starting with Geno. I don't think that the post-FP is going to be only third-parties either, I think characters from Nintendo like Rex & Pyra could have big chances. Sadly, I'm getting the feeling that the characters after the Fighter Pass won't be getting a stage to make things simpler, which makes me really sad: part of why I wanted Geno in Smash is because I want a Super Mario RPG stage with Super Mario RPG music. We'll see what happens.
That said, I don't know about Doom Guy anymore. While Geno's chances weren't too tied to the leak (as someone said, Geno could still had been a Mii outfit even if the leak was true) and he's being thrown around by leakers as a real possibility, I think Doom Guy's chances were hinging to this leak. If the leak was true he would BE a character, I don't think they would add a Mii outfit from a company that's not collaborating with Smash Bros. right now if it wasn't to add a character too. That doesn't mean if the leak is fake that Doom Guy won't make it in Smash, I just think he has lower chances to actually make it.