@Mr Gharial There hasn't been official confirmation on it, it seems they haven't definitely decided yet. At the Laafsekikkers it was discussed that the most recent direction seems to be sea turtles, sharks and large fish. Jellyfish tanks have also been mentioned, so those might also be added.
Antwerp does have a decent aquarium, but some of the larger marine species, especially the black-tipped reef sharks, are housed on the small side, and building a larger tank for these species would certainly be nice.