Almost 30 years ago, one of my coworkers thought that the internet would get so advanced that we would be able to stream videogames, and we wouldn't need consoles. I didn't think that this was realistic. I still don't. There is a huge advantage to having local hardware. For $400 or $500, you can get a pretty good gaming experience from a box in your home. It is going to be significantly better in 2020 with the next generation of consoles which are predicted to have about the same cost.
My 2017 iMac has slightly more powerful graphics than a Sony Playstation 4 Pro. The latest tablets and phones are also powerful enough to make good gaming devices.
AMD has plans to introduce new APUs in 2020 and 2021. This will make building a decent gaming computer cheaper, maybe costing $700 to $800.