Gaming

I'm confident in my "never" because of the capital economics; the service has to be expensive enough to pay for the infrastructure it requires plus some profit for the shareholders, while simultaneously being cheap enough to offer gamers a better value proposition than buying their own hardware. There's no margin between those limits, so the only market left for them to appeal to are niches where local rendering performance is limited but network latency and bandwidth are not. Even then, gamers still have the option of streaming from their own hardware using Moonlight rather than paying for a third-party service, so the only customers left are the ones with more money than sense.

Don't get me wrong, I love the concept (I even bought an OnLive microconsole back in the day and still regularly use a Steam Link to stream games to the living room TV), but it isn't nearly convenient or performant enough to justify itself as a subscription service.