Dave Kosak said that in an interview on the german site buffed.
No additional 5-man-dungeons planned, challenge-scenarios and Shaohao-lore - Interview with Lead Quest Designer Dave Kosak
Q: Do you even plan additional 5-mam dungeons for the rest of the patches of MoP?
A: No plans regarding that. There'll be more scenarios and you'll still be able to use the LFR tool for the previous tier of raiding. At the moment, we don't plan to release new dungeons.
I feared as much when they said that additional 5-mans don't fit the current raiding model.