Lengthy post but here is my thought right now regarding potential newcomers. This is speculation and not a leak. It may also be totally wrong knowing Sakurai but I am going off trends based on Fighter Pass 1. It also does not represent my "desires or wants."
First Party Situation:
I see three major first party IP in the running and all three seem likely to take 3 spots. They are the following:
1. New Pokemon Representative
2. Breath of the Wild 2 Representative
3. Xenoblade 2 Representative
I do think that if we get a first party in this second fighter pass, it will be from a game universe (not necessarily series itself) that is not represented already in Smash. This was the case with Byleth (Fire Emblem Four Houses is different world from other FE games) and Min Min. Therefore both for first party and third party, I don't see characters from represented existing series being let in. Nintendo is also going to want to promote new titles so the three above all fit that criteria similar to Arms and 3 Houses. Metroid 4 could also be a possibility but I see that as less likely.
Third Party Situation:
I definitely don't see a third party from an existing Franchise making it in. Based on trend from the first Fighter Pass, I think we will get a single third-party that is highly popular in Japan and another one that is highly popular in the West. I think the West gets only one character just like FP#1 with Banjo.
Here are the options that are popular in the West:
Rayman, Crash Bandicoot, Doomguy, Masterchief, and Geno
Out of all of those, Rayman to me appears to be the most likely. If Nintendo has less than the three first parties listed above, there could be a shot at a second one from the list but it would probably be more likely someone that is known both in the East and West. From that list, I don't think any of them are that popular in Japan. Maybe Crash and Doomguy but I would be (pleasantly) surprised if more than one makes the cut. I hate to write this as the list above represents some of the best additions to the game.
Sora - Sora is the elephant in the room and no brainer to be in Smash. He is iconic across the globe. However, I believe the rumors that Nintendo tried to get Sora for FP#1 and was shot down, likely by Disney.
Dante - I think Dante is highly likely, especially if we get at least 3 spots for third-party.
Japan third-party representative - It is going to happen. Let's face it. We are going to get a character that is probably not that popular in the West but will be popular in the East. I am not sure who that is because I haven't kept up with Japanese gaming as well. This website has a list of characters that I don't consider that bad:
http://cvxfreak.com/home/2018/12/17...y-representation-in-super-smash-bros-ultimate
The main Japanese character for FP#1 was Hero and I love that character. However, Joker also fit that bill and I wasn't a fan. So I was batting 50% there.
If I had to guess the roster, here is the best that I can come up with:
1. Pokemon character - I don't play the series but I can see one from the new title making it in. It will be probably a unique one from the current roster and will be a fun character
2. Xenoblade 2 - I think Rex is highly likely
3. Legend of Zelda BOTW2 - This is hard to predict as this game isn't out yet.
4. Rayman
5. Lloyd Irving or Dante
Overall, this wouldn't be a bad roster. If there isn't a BOTW2 character, I would say Lloyd and Dante both make it in. Both, although more popular in Japan, have a Western Audience so they would likely be popular adds across the board.
Crash and Doomguy also seem likely to take Rayman's spot but I am going to give the nod to Rayman for now.
If I could remove any character, it would be Rex lol but I think Xenoblade 2 is very likely to get a rep.
Edit: Geno is also a curve ball to me. He doesn't fit right now with the current setup but you get this feeling he is going to be in the game. I keep thinking he will be a bonus character... perhaps the last one. It is weird that his Mii Costume hasn't appeared yet. I stated Crash and Doomguy as likely to take Raymans spot but Geno could fit that bill as well. He does seem like the Banjo of this pass.