The qualifiers for Leipzig were played on the current map pool, but if the patch goes through as planned, players would be forced to play on new maps only three days after their official release. For now, they are available only in Melee modes — for testing. In their official post, Blizzard ask players for feedback on maps, perhaps indicating there might yet be changes to them before they are introduced to the ladder.
In turn, Blizzard have stated that Abyssal Reef, Odyssey, Ascension to Aiur and Battle of the Boardwalk would be removed. The first three have been mainstays in tournaments for months, so a sudden switch away from arguably the most standard maps might hit players especially hard.
As a result, a number of players have already expressed their frustration towards the decision.
CatZ, in turn, has written a response on Reddit defending the decision. Blizzard have not responded to the criticism thus far.
You can read Blizzard's update on the new map pool here.