Personally I like Sakurai choosing all the characters in Smash, and I'm glad that 99% of the people on these types of forums don't choose the characters. The reason is that I feel as though many people on here would only choose the biggest/most popular characters rather than Sakurai's methodology of mixing in both popular and unpopular (but still important) franchises in Smash.
Like, I would LOVE a fighter pass filled with Sora, Dante, 2B, Doomguy, and Crash; but it would kind of get stale expecting only expecting "big" characters in Smash. Thankfully, I feel as though Sakurai will continue mixing together fan-favorites (kinda like Banjo), currently popular series/characters (similar to Joker), and characters/series that may not be all that well known but have a big legacy.
So since a direct dropping in soon is a possibility, here are my predictions (not a wishlist), of who could possibly coming in the next fighter pass (assuming that it's a fighter pass to begin with). Overall, I think they'll follow through with similar kinds of characters compared to this pass (why change what ain't broke).
1. They'll start off with a character with pretty big popularity (financially it makes the most sense). I think that the most likely candidates here are characters like 2B, Dante, Sora, Crash, etc. This will be the second reveal in the current direct.
2/3. At E3, they'll do a dual reveal featuring a fan-favorite character (possibly a promotion like Waluigi) and a character that has a big legacy, but may not be THAT requested. I think Ryu Hayabusa from Ninja Gaiden is likely to be this character, however, it could be someone else like Professor Layton, or maybe even a Reimu.
4. They'll follow the footsteps of Terry and showcase a character that may not be that big, or have that well known of a series; but may belong to a series with some legacy (similar to FF/KoF); these are the types of characters that not a lot of people are predicting. I think characters like Monokuma from Danganronpa, Adol Christin from Ys, Laharl from Disgaea, Estelle/Rean from The Legend of Heroes, Travis Touchdown from No More Heroes, Sol Badguy from Guilty Gear, and Ragna the BloodEdge from Blazblue.
I know that there are some people that are predicting/have these characters on their wishlist, but these characters aren't all that well known to the majority of the Smash audience/general gaming audience; I guess Adol has the biggest legacy of these characters, and Monokuma is the most popular one in terms of recognizability outside of Japan. Inside Japan, most of these series seem to do similar numbers to each other; which is why I put each of them in this position. The exception to this is Travis Touchdown (NMH isn't anywhere as popular as the rest of these series in terms of sales), but Nintendo seems to heavily pushing NMH so Travis gets points for that.
5. I have no clue, because there is no one to go of off yet. Consider this a wildcard; I'll just put Neku from The World Ends With You here, because that is my personal pick.