There was nothing in the article that said those were the only heroes who would be included.
Yea, Superman, Batman, Wonder Woman would be the most ommonly known ones, nd of course Green Latern (wether you liked the movie or not) is now very well known due his own movie. Flash, hasn't had any TV or Movie exposure in alot of years, other than possibly Animated, and Aquaman Pilot never went anywhere, so, no reason to spotlight those two, since thy wouldn't be as well known as the other 4.
One Day I hope to be the Man my Cat thinks I am
Where are we going? And why are we in this Handbasket?