I'm still watching, but as for Superman-actor sightings, I think we're more likely to see Brandon Routh than Dean Cain on the show.
I'm hoping we get to see Supergirl's Superman again; I like Tyler Hoechlin in the role.
Joy,
Lynn
I don't really like what they're doing to Ray (Brandon Rouths's character) on Legends of Tomorrow to be honest. He's supposed to be an actual super hero in his own right and a darn good engineer, right?
He was all of that on Arrow, and for a while on Legends of Tomorrow, but now he's mostly the comic relief and playing second fiddle to the neanderthal on the team.
As far as as sightings go, Brandon is much more likely to show up on Supergirl. He plays a character on a show in the same multiverse with a bunch of crossovers, so bringing him in won't cost that much extra. But to be fair, he was on Arrow before Supergirl premiered.
I also really like Tyler Hoechlin as Superman/Clark.