Just wondering, are there any rumours about why they are uniting the Justice League? it can't be just because of Luthor right? Is he that big a threat that they need 7 of these superheroes? I haven't followed the comics.
It's highly unlikely they're all joining up to fight Lex. If I were a betting man, I'd say they're going to recreate the Dark Knight Returns Batman/Superman fight, but instead of Green Arrow providing backup, Bats is gonna get WW and Aquaman to take out Supes (or atleast keep him busy).
That said, yes, Lex can very much be that big of a threat. Just maybe not from the get-go.