On the subject of Kratos being one possible contender
People cite the whole crossplay thing as Sony finally opening up and being more accepting of other companies and being buddies but don't forget, for the longest time Sony was absolutely stubborn in its refusal to allow crossplay and to keep its players within the Playstation ecosystem. It took the combined might of everyone pestering them for a whole year and even game devs calling them out on being stingy for them to finally go "Alright, fine, geeze, here you go!"
They opened up crossplay, but they had to be dragged kicking and screaming over to the big button they needed to push. It feels like Sony being 'friendly' is doing this through clenched teeth. Oh, let's not also forget that Sony wanting to hoard Persona all to themselves is the reason we still don't have P5 on the Switch, and we're only getting the spin-off
Microsoft on the other hand proved they were willing to go the distance with its friendship to Nintendo; with Minecraft, Ori, and Cuphead, and making crossplay the cornerstone of their new relationship. In fact, it's because of them that Sony was suddenly catching heat! That's why we all pushed for Banjo so hard, we knew this was the time to make it happen and it did.
So... I'm kind of doubtful that they'll give up a first party IP like Kratos to join Smash Bros.
Crash is a slightly different matter since even though Sony is waving him around as their returned mascot, he's a multiplat franchise and owned by Activision. I'm very confident he's inevitable at some point.
For right now though, I feel like Sony will sooner make a PSABR 2 then let Nintendo take one of their characters.
But hey, crazier things have happened! I could be totally wrong!