As someone that plays mostly on handhelds and currently uses the Switch as my primary gaming platform, I would love for something similar to what the OP said to happen (I also wouldn't mind seeing a portable PS4, since there are so many PS4 games that I have but do not really have the time to dedicate to).
There are a few elaboration and changes I would make to the strategy proposed here. The critical elaboration I would like to make is that the Xbox One portable is going to be compatible with the existing and future Xbox One library (and the same would apply to a hypothetical PS4 portable). This is important, because as we have seen with both Nintendo and Sony, it is very difficult at this point to support two completely different platforms and have enough software output to satisfy both handheld and stationary system owners. This why Sony sort of left the Vita behind in order to focus on PS4, and Nintendo did similarly with the Wii U in favour of 3DS (and of course now with Switch they are mostly focusing on a single platform). The issue is that production values for both portables and stationary systems are increasing, and that demands increases in development resources in order to support two platforms. By Microsoft having the same architecture as Xbox One in a portable they will ensure that new cross-gen titles as well as less demanding games come and that players have access to a robust library of games that have already been released.
The first change I would make is to the proposed specifications. I don't believe we need something as powerful as an Xbox One X in a handheld. Looking at what technology is available right now and what the road maps look like, we will most likely not be getting a mobile chip that gets anywhere close to a One X in the next 10-15 years. On the other hand, a mobile system that is about as powerful as an Xbox One should come into fruition within the next 10 years and I think that will be enough. A 6"-7" screen at 720P-1080P should be more than sufficient at regular viewing angles, putting 4K on such a screen (provided that you do not want to do VR using the same screen) would be overkill for a portable. I have seen 4K screens on Sony smartphones and 1440P screens on most modern smartphones, and the difference at such small screen sizes to 720P-1080P displays is really negligible. Now you might say that the 4K would only be for a hypothetical TV mode, but I would ask would we really need a 4K TV mode for games so urgently for such a device, particularly when the OP wants to compliment the system with a stationary TV console that will likely do native 4K.







