There is one tiny problem with your wild theory, 11.0.7 PTR is already up for weeks and nothing suggest there is something wrong with schedule. Stuff could be cut from patches, release may be rushed and full of bugs, but looks like for post-SL Blizzard this "patch every other month" rule is sacred.
Not to mention "something they never did in recent years" was literally during last small patch, 11.0.7. Siren Isle was in December, Turbulent Times early January, Plunderstorm mid January.