The reason sbar was nerphed at the beginning of the expansion was because it was moving ahead of sblock. Blizzard saw a problem with this and intervened thus we got a sbar nerph. Unless blizzards philosophy has changed in the last 9 or so months I would expect to see sbar nerphed should it push sblock out of our rotation.
There is a lot of confusing messages from blizzard regarding prot warriors. They want us to use sblock but have publically stated they are worried about us getting crit block capped. They introduced riposte but don't want us to take a avoidance -> crit -> sbar build as demonstrated by their previous nerphs. Outside of simply denying us mastery gear I am not sure where they plan to put the carrot to achieve their goal with prot warriors.