My serious, 100% opinion is that we're going to get a one-off newcomer trailer in October, similar in vein to Robin and Lucina's, and then a Smash direct with two new chars and a few echoes in November. Then a huge maybe on a newcomer reveal in December, right before the game launches. No idea on who would be revealed, but in my opinion, with what characters people are deeming likely now, I'd see it as something like this:
October: Incineroar/Gen 7, maybe a possible echo reveal to coincide with the similarity to the Robin/Lucina trailer, in this case I think it'd be Ken, who might be shown fighting Incineroar in the trailer
November: Shadow could be one of the new echoes, or he could end up being an Isabelle-style partial clone, or end up being a completely unique fighter. Who knows at this point, Isabelle's throwing me for a loop. I think he is still likely for a potential November direct.
Aside from Shadow, I also feel at this point that Dante is pretty likely. And with one of the two anons explicitly saying that he's for November, I'm inclined to put him here.
If Shadow does end up being an echo, then I think the other character revealed could be Isaac, IF Geno is in. If Geno isn't in, then it might end up being the reveal of the "SE rep" from Verge's leak.
No idea for December. I'm inclined to say Geno if he's in, since he would be pretty fitting for a final reveal to cap off the pre-release hype season.