If they keep going this way, it's probably only a matter of time before a common "gaming box" standard is set and these companies just become manufacturers against this standard.
It's happened before to various levels of success.
Already tried by Steam with SteamOS and Steam machines [1]. They even developed a custom controller. I haven't heard much about it since its launch roughly 5 years ago, however I would assume it is all but dead now.
It was tried at least a couple of times (3DO and Steam machines) but it failed for various reasons, I think mostly because the result wasn't very cost-competitive with proprietary consoles.
Yeah, and others: MSX, Nuon, and the modern PC compatible systems.
However, outside of gaming (and even computing), it becomes very common once it's no longer a differentiator to build your own version of a thing. Consider VHS, DVD, shipping containers, standardized faucet fixtures and so on.
It's happened before to various levels of success.