Every major player, minus Nintendo, is entering or already in this market. Most notably, Microsoft is releasing xCloud very soon, and PSNow already exists. You can go play God of War, a PS4 game, on your PC, literally today (unfortunately, no Mac support yet). Its $10/month. No one talks about this!
Realistically, the cloud gaming market will become a utility, just like the cloud itself. Who can provide the most datacenters as close as possible to large customer bases? Who's technology provides the best user experience? Who is available on the most screens? These are all questions that multiple major players can have great answers to. Stadia was "early" (though, Playstation was the earliest, and its not even close; they purchased Gaikai in 2012 and OnLive in 2015, they're so far ahead that Google wasn't even thinking about this when Sony was actually selling it). But a player being early means nothing if this thing that Stadia released today is in the state that its in; they need years to iterate on it.
So, what will differentiate? The Games! This is the Hard Problem in this space. Not networking. Not DC locations. Games!
The choice isn't just "do I want to play RDR2 for super cheap with decent quality on Stadia, or in great quality but a $500 upfront fee on my X1X". There's a third choice there: Should I play it on PSNow? xCloud?
And, realistically, yeah its a very fluid market. I could play on any of them. But Microsoft, Sony, and Nintendo are destroying the third-party AAA game development space. Their first party studios are insanely good, seeing billions in investment and new acquisitions. They have proprietary world-class technology that they only share internally (example: the Decima engine used in Horizon: Zero Dawn was used for Death Stranding, and is widely considered to be among the most technically advanced engines in the world right now (though, Kojima isn't an SIE Studio, so maybe its a bad example)). Point being: if I pay for Game Pass on Xbox, and I'm a big fan of their exclusives, then RDR3 comes out and I can play it on xCloud, I'm going to buy that on Xbox. There's gravity to these platforms, and that gravity comes from the titles where I have to go to xCloud to play.
Phil Spencer, head of Xbox, has the most measured and strongest position in cloud gaming. At E3, he said that he sees it as just one avenue where people will play games. In some situations, it makes sense. For some people, it makes sense (though, those people like you will never play games as much as people who have consoles/gaming PCs). So, they will build it. They have the technology and DC footprint. But, Stadia's downfall will be in their all-in approach, combined with their lack of revenue strategy and lack of first-party exclusives to build gravity.