I very much dislike the idea of the Colony, but there is absolutely no reason they couldn't return. One of the staples of comics is how easily reversible everything is. Superman died. He came back. Ras Al Ghul died. He came back. Batman was displaced in time. He came back. The Titans disbanded. They reformed. The same is true of the Legion of Doom and the Fearsome Five. And H.I.V.E. And pretty much everybody.