Could do what WoW did.

Mythic is delayed release, but so is LFR. Normal/heroic release immediately. LFR is a week or so after. Mythic is a week after that.

Not entirely 100% on the mythic timing as my guild couldn't pull 10 more folks out of our ass for it(despite doing mythic/heroic np in MoP), but they've done the delayed LFR release for a while now.