At this point, only one group of video game characters (from video game franchises, keeping "loophole" characters Android 21 and the New Kid out) remains yet to have anything resembling a form of presence in Smash Bros.: Sony characters. (Crash and Spyro, now owned by Activision, do not count for the purposes of this question: for a good reference on which franchises are legit owned by Sony, check the PSAS wiki's Franchises template, the first party lineup).
What are the chances we get one of them? Do Kratos and friends occupy the impossible tier like Goku and his gang, or is there a chance that they might show up? Who would it be, or at least who would the second character be if you think Kratos is nothing short of a lock for the first one? Would you want to tap into that library?
While I'd love to see it happen one day, unfortunately I consider it a Goku-level pipe dream. On an objective scale I think it has to be Kratos, but if I could choose based on a combination of bias and reason it'd be PaRappa (pretty much, this dog's the reason rhythm games are much of a thing, he's got DQ cred for another genre) and if it was pure bias it'd be Sly Cooper easily.
I'm gonna go on a limb - and not just because I want to be a little different:
I don't see Sony as Goku-level of impossible. The tier or two "above" Goku, certainly: where they are practically impossible, but not quite. There are a couple things going for a Sony characters chances:
* Ken Kutaragi is long gone from Sony at this point. He's the guy who spearheaded the PS1's development, the SNES's sound chip and helped build the SNES CD-ROM. If anyone, he's the guy who would oppose any sort of partnership with Nintendo the most, since Nintendo's behind-the-back deal with Phillips enraged Kutaragi. To the point that he convinced the other Sony execs to focus on the PS1. Ditto a lot of execs from the PS1 era - they're not at Sony any more.
* The pressure on Sony regarding crossplay is slowly taking its toll on them - with CoD Modern Warfare and PUBG getting crossplay between PS4, Xbone and PC.
* PlayStation AllStars is dead and buried, and it'd be difficult for Sony to reestablish their own fighter.
* Finally, the infamous Sony email hack led to
rumors that the Super Mario Bros. movie would be produced by Sony - when emails between Sony exec Amy Pascale and movie producer Avi Arad got leaked. Pascal apparently forwarded her email to infamous Sony exec Tom Rothman*. Of course, things either a) didn't work out in the end considering the movie's now with Universal (and Illumination) or b) was not true to begin with. But if Sony (even if it's their film department.) was willing to make the Super Mario Bros movie, they're not as antagonistic to Nintendo as they were during the PS1 era.
What would need to happen is something near-impossible: Sony either embraces crossplay, or the PlayStation falling from grace massively. Not seeing that happening in the near future when the video game department's run more competently.
If we're getting a Sony fighter, I also think Kratos will take priority (Dad of War was a major boon to him character wise), with Jak / Daxter, Rachet / Klank and Nathan Drake not far behind. Personally my wishlist would include Sly, Parappa, Kat or Sweet Tooth. With a WipeOut Assist Trophy.
*(Incidentally, Rothman's also behind masterpieces like the Emoji Movie.)
