I think the rework is going to disappoint when it eventually happens, and it is years away.
Timeframe wise: I don’t think were going to see any Priest rework this expansion, it will all be tuning until next expansion and there may be a rework at that time, though I would still call it doubtful for one main reason. Priest is bleeding its player count, and its only speeding up despite having two of the healing classes, which usually meant it had a very respectable % of total population.
When the re-work comes its likely it wont be great news and the reason for that is purely based on Augment Evoker being a thing. The Augment evoker fills a DPS slot, is accepted by the player base and has mod representation to account for its low personal DPS output while being a semi-support or Soft Support.
A priest rework is going to hit the same way; when wow first launched priests were pure support. Shadow was basically useless for DPS, holy and disc were both meh with some minor niche moments they could really shine. WOTLK was the first time Shadow was truly a DPS and really it was only by the end of the expansion that it could do this. It languished after WotLK until Legion, after that its been all over the place in all three specs and as we all know its basically been abandoned by Blizz since, and when they do speak on it, they always point to the other aspects it provides being the things that should have value.
So a priest to Blizzard is: Stam Buff, Power Infusion, heals from shadow or DPS from disc. Its design has been to be the bottom performer in its designated role while also being a bottom performer in the other roles.
Shadow is low DPS but it brings a Stam buff, power infusion, Vamp Embrace, Leap of Faith, Halo group heals, the worst interrupt in the game and lots of personal sustain.
Disc is the opposite with the low healing but tons of other things that make up for it, but it took many expansions and updates to the mods people rely on to account for the utility it brings outside of healing throughput.
The rework is going to make either Disc or Shadow the next Augment evoker and the changes to shadow in TWW are indicating that they have chosen Shadow for that rework. The DPS will remain lowest possible and the rework will focus on buffing the utility aspects.
Disc and Holy will likely just be reworked to reduce button and Talent tree bloat but largely be unchanged on the basic designs.