PS would still be the best selling console. It's the most popular in more of the world than any other console already so considering brand name would now be one of, if not the, biggest factors it would be the best placed to do well.
Nintendo, if they still sold consoles, would still do well, for the same reason as PS, it's popularity just isn't as wide spread. To be honest I think they're the least likely to still make consoles if everything were fully multiplatform though. They'd probably take the biggest hit sales wise, as in more people buy their consoles for the exclusives than any other console. And the incentive doesn't seem there for them as much. They're primarily a software company, compared to Sony being a hardware company.
Xbox would still exist, but it wouldn't even be in the running for top selling hardware, guess it isn't now either, so there wouldn't be much difference.
Bet Shiken that COD would outsell Battlefield in 2018. http://gamrconnect.vgchartz.com/post.php?id=8749702