The market is full. There’s really no other way to say it. Anyone short of Apple, Google or Amazon themselves pouring hundreds of millions of dollars into a huge new console launch is bound to end up dashed on the rocks.
Debuting a new console in the current, already crowded market is pretty much impossible, which is why you have not seen even other tech giants enter the market. If Nintendo decided to pack it up and become a software company only, or Microsoft decided to fold the Xbox brand, sure, maybe there would be an opening. But neither of those things are close to happening, and a fourth major player in this space would arrive and promptly walk straight off a cliff.