I guess the main reason why blizzard added "interact with target" in wotlk was to make it easier to talk to NPCs. Not sure how it is nowadays on retail but on older Xpacs it often happend that some NPCs were so crowded with players that it was quite hard to right click on these NPCs to talk to them. Some ppl were even intentional staying with their fat mount inside the NPC so nobody can talk to him.

On Vanilla u have to talk to the NPC in order to queue for BGs so I guess there will also be this NPC blocking issue.
So maybe there is hope that they will add IWT as a quality of life additions to vanilla which would make melee boxing possible.
I think they will also add dual-spec as a quality of life addition.