From the sounds of it, you will be able to play all new games on all forms of new hardware they release. One console will be for streaming(cheapest entry point), another console will be a discless Xbox One X(cheapest 4K entry point), then there will be the Xbox One X2, and then probably a discless Xbox One X2(a cheaper version of the latest console).

If this is their strategy, then they aren't fragmenting the user base at all, particularly when you consider that all of these consoles will be backwards compatible with all of the Xbox 360 and original Xbox One games. On top of that, the Xbox One X will still be relevant, since it's specs are still rather good, and will probably be the new baseline for next gen, just like the Xbox One S is for this gen. It's still also possible that some developers, even if it's mostly indie developers, will continue making games with the original Xbox One minimum specs in mind.

Beyond all of that, Xbox Live is a continuous experience across all Xbox consoles and PC, including party chat, and from that stand point, the userbase is never fragmented.