This wont happens.
It is all about Nostalrius Begins policy: blizz-like vanilla.
"Blizz-like" actually allows some adaptation, like choosing the version of a dunjeon or BG to be earlier to 1.12 for example.
But changes that occurred at Burning Crusade or after will for sure never be implemented.
And also, we are a lot of player actually enjoying the high respec cost. It gives a sense to a lot of specs. Pure PVE HL players will go for a PVE raid optimized spec, and sacrifice efficiency in PvP. Casual players can go for mixed specs, that is ok for raids, PvP and farming. This respec cost is what brings a lot of diversity in vanilla
