Outside of PlayStation the progress is likely to be drip fed progress wise. There was talk of the Vive Pro Eye tracking tech potentially being an extra people can buy for their current headsets further down the line. This is something we have seen a lot of from the PC biased headsets already.
There will still likely be big leaps, an example could be light field displays, we a still a long way off from them but if that was to be added to future VR headsets that would be a big change. Generally outside of that FOV, pixel density or resolution and any other bits and pieces could either be done as add ons or hardware iteration similar to that of phones rather than big generational updates. This makes far more sense due to them being in contact with the body.
Having a PSVR since launch I'd like for any future models to have a bit more flexibility in their upgrade path simply because it's a wearable and the wear and tear is different from a console and not as cheap as a controller to replace if a lens gets scratched or the headband padding comes off.
I think your reply and Krejlooc's may have read more into the "generation" comment than intended. Yes, it will be an incremental step up, but both the Rift and Vive are going to be hitting 3 years old soon. There's been some mid-gen upgrades, like the slightly lighter Vive, the Pro with the 2.0 Lighthouses and depth camera, and the Rift Roomspace and Touch Controllers, but for such a rapidly-changing and improving technology, these products haven't seen a full update yet. I've heard hit-or-miss things about the Knuckles controllers, but I think it's silly I'm still waving around big ol' Vive Wands while Oculus users get their smaller, more flexible Touch controllers. (I know I can technically use them, not the point.) Video cards just launched with a new connection standard designed to make VR hook-up more simple, but nothing actually uses it yet. Eye-tracking is a Now thing, not a 5 years down the road thing (as you pointed out, you can buy a Vive insert right now in China), and is both more immersive in single and multiplayer, and is the key to lowering hardware demands with foveated rendering on higher density panels. The normal Vive still ships with the 1.0 Lighthouses and no Deluxe Audio Strap standard, I just checked the site and some retailers. Both headsets could learn some comfort lessons from the PSVR, which lets you easily flip up the visor without any after-market 3rd party straps. And again, Valve's got something cooking, as Krejlooc probably knows. It's likely whatever they plan to do is coming timed with a BIG burst of content.
It's smaller stuff, but it does all add up. And sure, it's more akin to a video card upgrade, but those can be nice too. Especially if it's been a while since the last one.