Well, a new empire could come up. A new faction could be basically an old faction falling into two halves due to internal struggle. it is not impossible. It does however require a story in which the factions and generals are changing over time, like they did with Doomtown. In the Doomtown game, every expansion, big or small, furhtered the story. This meant that certain unique characters would get a new version over time in line with the story. Or that cards referenced key events, like the massacre that occurred during election day of the new mayor.
A new general seems like a matter of when, not if. When they get the current generals in line, then there might be some consideration for a new general.
Also, I like Starhorn. He is fun with Sphynx and cooky decks that have elaborate combos in which the extra card really matters more to you than to your opponent.