I saw the destruction starting a couple of Mondays ago while transferring from T8 to T6.

With a bit of imagination that was certainly lacking, this glass wall could have been incorporated into the new architecturally insipid T8 which features the modern day "me too" I have a swooping roof (found at JFK T4, KIX, LHR T5, et al.).

As for the question of what was supposed to be built in place of the venerable AA terminal, that was to be a larger new AA terminal. This new terminal was cut down to about half size, and evidence of those cuts can be seen at the terminal upper roadway where there is more roadway than terminal frontage. Inside, the east wall with the mural is a wall that should not have been there if the terminal had been built to its full extent as that wall represents the center line of the original dimensions of the new terminal.