I'm sorry, but I just cannot figure out how decisions are made in the TV and movie industry.
The most-watched episode of Smallville this season was the one which featured Arthur Curry (aka Aquaman). Arthur (or A.C., as he was referred to in the episode) was played by Alan Ritchson, who certainly had the look and played the part with an aggressive and confident streak which suited the character well.
So of course the just-announced series Aquaman, which will feature the title character in his 20's and before he goes by the superhero moniker, will not have anything to do with the character who appeared in Smallville nor will it use the same actor to play the part.
Also, in order that this will make even less sense, the show is being developed by the producers of Smallville and will air on the same network.