Apple won't enter the console race. Any console from Apple would be overpriced.
Amazon or Samsung are more likely than Apple, but that's still a long shot. Out of anyone I'd put money on Valve entering the ring.
Bring back the Steam Machine. A dedicated box that has access to almost the full Steam library on day one would certainly get my attention, depending on how much it costs of course.
There is zero chance Samsung goes into the console business.
A Steam machine is a reality, but it's hard to really classify it as a console, though what a console is has changed so much that it closely resembles what a Steam machine might look like.
A Steam machine has a lot of advantages in that the online play would be free, it has all the games, presumably would have Steam VR, but it also has a lot of weaknesses.
Valve doesn't make a lot of games, a steam machine is going to be overpriced because Valve can't sell it on short margins and Valve's software royalties are less than Sony's. Being all digital, it'll struggle to find a place in retail.
If Valve does come out with a Steam machine, I think Sony's PC strategy will change immediately and it will accelerate their plans for a PC Storefront.