The best players in the world will still be the best players in the world, but in the past the most elite guilds have deployed support teams to continuously develop and refine DBM/BigWigs/WeakAuras during the RWF to give them any possible advantage.
It will be interesting to see whether they are able to work around some of the obstacles created by the “disarmament” of addons.
There may be in-game ways of communicating or extracting secret information, although I think a lot of time has been invested in eliminating them. One interesting thing will be if the RWF guilds keep (more) parts of their UIs hidden in streams, to avoid revealing any “innovative” tools.
But in-game workarounds (which could cross the line into exploiting) may not be neccessary. There is no rule (AFAIK) against using out-of-game technology, like having a “co-pilot” (human or automated) monitor every raider’s screen and feed real-time data into a boss-specific utility program, which in turn sends information back to the raiders via an overlay or second (out of game) screen, and audio feed.
If this sounds silly, they started down this road long ago, by having a dedicated raid leader who directs traffic from outside the instance. The “copilot” technique would just (effectively) give each raider their own assistant raid leader “advisor” (a human WeakAura…), and move the information sharing and communication (provided by DBM/BigWigs in the past) out of game.
Of course, the RWF guilds could take the opposite approach, and strictly limit themselves to only the weak-sauce tools that remain available to the rest of us. That would seem out of character, though.
Not only are the guilds moving into uncharted territory, but so is Blizzard. The apocalypse almost certainly makes it more likely that encounters will be over- or under-tuned, since a lot of past experience has been invalidated.
It should be interesting, or at least amusing…