The blue post linked above includes Blizzard's thoughts on ladder map pool, but it's not worth to translate all the words and I don't have enough time to translate that right now. GSL maps are only mentioned once on that post; GSL maps(soon): Macro-oriented.
Here's short translation: We're going to maintain the number of ladder maps to 9 with 3 macro-oriented, 3 aggresive and 3 intermediate maps, so that a player can thumb down based on the player's preference. GSL maps(soon) are macro-oriented.
The news is what I said on my stream a month ago; PMLTAWMGN.
W: Will (be)
Updated 1 22:29 8 March KST
I just talked with reliable source and he said Terminus RE is going to be added first.