The easiest way to make this work would be to have the final raid involve going to this "timeless" place, because canon-wise, it can be assumed all player characters participated in said raid (even though obviously most don't).
However, this would require a full-world revamp to come in 10.0, and I'm incredibly skeptical that that will happen. Even with the larger team WoW got in response to the issues with Cataclysm (and it's even larger now), the idea of revamping the entire world in a single expansion (which they'd need to do, to do a timeskip) is completely wild effort-wise.
The only way I could see it is if they decided to return the "main" WoW world to a sort of "resting" state as it was pre-Cataclysm. Pre-Cataclysm, stuff was happening, but little of it seemed particularly urgent or changing across the world as a whole. It was all slow and largely static (as makes sense for a long-term MMO). For reasons which have never been explained and are hard to explain except with "high as balls the whole time", Cataclysm threw that aside, and made the main world be in a very specific moment of time, days to weeks after the Cataclysm. A few zones were slightly more timeless, but most are "Shit just went down!!!! FIX IT!!!" to a greater or less extent. So you revamped the world to be more steady-state (not utterly static, but like, durable) in a time-skip, you could have a situation which was more enduring, and could be altered on a zone-by-zone basis as necessary, but never again needed a "full revamp". This would be good for WoW's long-term health, I think, particularly if future expansions are to be set on Azeroth.
But it'd be a big investment, and I'd expect to see them hiring already if they were doing it for 10.0.