They won't need them though, like streaming services we're entering an age of self reliance and conglomerates. Sony is heading this direction as well as they have to but their issue is a lack of financial capital which could potentially sink them long run.
I think Sony will always have 3rd party and a broad range of content, there's no need to be the same as Xbox.
They can offer different things. Plus 3rd parties wouldn't be happy about how much they would lose.....