With the release of WoD Blizzard claims to be wiping 20% of each classes abilities.
They will not be adding any additional abilities while leveling 90-100.
They could do 1 of 2 things:
1) Mangle removed, shred baseline has no positional requirement.
2) Shred passive buff between 90-100 that removes the positional requirement.
Personally I'd prefer the former, and save the passive buff for something a little more interesting.