They need LESS shaking things up the formula, not more.
Every time they radically depart from the formula, the results range from "absurdly horrible and dropped for all future expansions" to "stuff that's more-or-less okay, but not as well liked as the main content."
They've yet to outdo the core dungeons/trials/raids/24-man/Extreme/Savage stuff, and I don't think they should even try.

... which is WHY people more speculate on where the story's going, what the new jobs will be, etc.