Even if Days Gone isn't going to be generation defining like something like God of War was for instance, I still expect it to turn out to be a good to very good game.I want it to be successful but not so successful that they make sequels. Open world zombie games like this have never interested me, I'd like to see them making something else.
I also expect it to be very successful financially, securing their position among Sony's studios, while allowing them to expand further for Days Gone's sequel as well as the new IP, that they are apparently already hiring for (though I'm still sceptical about that).
All of this seems very positive to me. We are essentially witnessing the rebirth of a AAA studio for SIE.
In any case, I expect about inFamous SS levels of success for this; low 80s meta and a few million sold.