Looks like they are.
(http://www.mmo-champion.com/content/3718-Patch-5-4-7-PTR-Build-17807/)
Why would they waste resources on new models for a filler season. Those take them months to design.
The one thing I wanted to point out is that it is not confirmed by Blizzard and the statement: "more MoP content would slow down development" tends to favor the opposite. So basically this is pure speculation and not a fact.
Maybe it was planned initially, but the latest info on that says:
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"Another MoP patch would delay WoD, so Patch 5.5 isn't going to happen. The entire team is working on WoD right now, so any more MoP content would slow down development."
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Source
"confirmed by blizzard that they are creating a new mid-range raid" before WoD??? As far as I'm concerned there won't be any new raid content, even a small content patch is unlikely!