Board Thread:News and Announcements/@comment-807326-20150413110105/@comment-1330227-20150603215546

Wraiyf wrote: Although recently it was confirmed that CBS WILL NOT allow crossover between Supergirl and Arrow, so it's unlikely that TW will allow a cross over with Arrow either.

No, it's not confirmed. CBS Entertainment Chairman Nina Tassler said, "those two shows are on a different network. So I think we'll keep Supergirl to ourselves for awhile." That is the only thing close to official that we've gotten, and it says 'for awhile.' That means they may crossover later.