do Dr. Nefarious! I so want him in!
The reason that this took quick it's because I have bad news for you friend, you're gonna have to wait for the next game.
The reasoning behind that: Ratchet and Clank already represent the series and they probably aren't going to have too people for one game series untill the sequel is made. Dr.Nefarious does have a high probability for the sequel however because that's when they will add more characters from the same series (Like SSB). Another reason is beacuse he isn't really the most requested for this game.
Final Conclusion for Dr. Nefarious is: Wait untill the next game.
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Gex is a strange case, he is a somewhat requested character, but he has always been a 3rd party character.
With the leak in mind and the remaining characters left(only a few), I have to say no to Gex and here is why:
Gex was actually a 3DO exclusive for a little with the Playstation port of his first game coming later. Now you may say, "Isn't that like Crash? Crash is 3rd party." but he isn't as requested and isn't as associated with the Sony brand. Although I do think he could be a cool addition to the game, I don't think he is there. He does have a case for the sequel after SB gets the "Sony character roster" down, I think he could be in the sequel, sorry
Final Conclusion for Gex: No, with a possibility for the sequel.
Cloud seems obvious and this will take a little to explain, but my conclusion ends with a scale, because sadly, I can't get a definitive answer to this(which has pros and cons).
Cloud first appeared in FF VII which is a great PS1 exclusive and is even considered to be one of the best FF games. There was a PC port a year later technically making this game 3rd party, but it is lesser known about which is a good thing. Now Cloud being the main protagonist of this game boosts his chances of getting in this game. He is also a character who gets requested A LOT which helps greatly because SB said fan suggestions is what kind-of builds this roster. Paul Gale also has a hint that leads toward him. However I have no definitive proof he is here that is why I have to use a scale from 1-10.
Final Conclusion for Cloud Strife: 8/10, 8 means really likely , but there still is an off-chance .