At this point, we know for sure that Xbox is working on a next-gen console that's currently known as Project Helix, and that it will support both console and PC games and be an actual first-party console developed by Xbox in-house.
However, there have been rumours for some time that AMD's chip for Project Helix may be used in other ways too, and that Microsoft may essentially offer more third-party devices in the Helix lineup throughout the next generation.
The latest rumours about this come from well-known leaker KeplerL2 on ResetEra, who responded to someone suggesting that the Helix chip will be available on "other machines" by claiming that although it won't be sold directly to consumers, the likes of ASUS and MSI could make machines based around the chip in the future.
Xbox's VP of next-generation, Jason Ronald, then responded to a tweet about this with the following:
As you can see, Ronald wants to make it clear that Xbox is definitely developing a first-party Project Helix console — something that will surely serve as the centrepiece of whatever the Helix lineup ends up being over the next few years — but he didn't address whether the Helix chip will be used in other machines as well.
We assume any third-party devices wouldn't take the form of actual consoles, but rather third-party PCs and potentially more handheld PC devices too, but ultimately it's anyone's guess — it's all just rumour and speculation for now.
For what it's worth, KeplerL2 speculates that when it comes to Xbox backwards compatibility, nothing but the first-party system(s) will be able to utilise "actual Xbox BC" due to licensing issues, so we could be looking at a situation where any third-party Helix system will be a more lightweight version of the actual Xbox Project Helix console.
Let's see what happens, eh? There are too many unknowns right now, and all we know for sure is that Xbox's first-party Project Helix system is on the way, and it should be an absolute powerhouse for playing both console and PC games.