We may never get Superman or Batman or any of the original Justice League heroes other than the Flash on the Arrow-verse’s Earth-1, but we can always count on mentions of anybody and everybody from DC history coming from the time-twisting Legends of Tomorrow.
My only disappointment in the Man of Steel mention is that former Superman Brandon Routh wasn’t on hand as Ray Palmer to witness it.
Of course, we shouldn’t take Barnum mentioning “Man of Steel” to mean that Superman has been active on Earth-1 ever since Arrow kicked off the Arrow-verse back in 2012, but the quick name-drop was definitely fun.