Canceling buffs are only restricted during combat.As it is now SW needs a cancelaura both shields in order to break sheeps/blinds and with that anounce we won't be able to cancel them and a big skill factor in pvp will die.
Fairly sure this refers to the earlier change that made buff canceling a restricted action making it impossible to right-click buffs off yourself if you were using an addon to handle your buffs. It sounds like you will now be able to right-click them off as long as you're not in combat.
This change only refers to add-ons being able to cancel auras once again (when OOC). This is important for chicken/grenade/whatever removing add-ons.
Players are still able to remove buffs in combat.
Btw there's already been a nerf to shadow word death'ing everything. You could SWD through shields in WotLK, now you have to cancel aura (like it has been in TBC, I think).