I wouldn't be surprised if 8.0 gives Shadowbringers for free

[Oizen]

The game gets too expensive if you're expected to buy every single expansion, It would just be a bad look to see a ~$300 price tag, so slowly turning them to free content prevents that from happening.

[MistakeNot]

The game gets too expensive if you're expected to buy every single expansion, It would just be a bad look to see a ~$300 price tag, so slowly turning them to free content prevents that from happening.

You aren't expected to do that - unless you are playing for years and buy each expansion when it first appears.
Buying the latest expansion gives you access to all the earlier ones too, so a new player will just have to buy the base game plus whatever the latest expansion is at the time to have access to the whole game.