That's the only reason I can think of. I can wait, I mean I will be pvping on one of my few 50s in ranked, probably on both sides. I do it all the time, save the few nights a week I raid and this delay doesn't bother me. They want to give us the biggest bang for our buck, so I say let them.
I mean I am already floored at the good decision making it took to keep rated armor sets at the same stats as unrated. So, kudos and keep it up is all I would say to them.
There's plenty of things for me to tool around with in 1.2 without ranked WZs!