Let me see if I can "justify" my choices:
The Ancient Era: So, let me see if I have this right. I can either play a god-like lizard doomed to be hunted down and exterminated by my insane clone-father just because I've been making too much "noise" to suit him, or I can play a transplanted, and possibly genetically engineered, survivor of Armageddon who has to try to build a new civilization from a smoking pile of ash, all while trying to avoid being killed by one of the Gods-War weapons that's still running around? Thank you, but no.
The Ziru Sirka (The First Imperium): I already work in a mindless, possibly pointless drudge-job in which my bureacratically appointed overlords attempt to quash even the slightest vestige of indiviuality. That's why I game. That's why I don't game in settings that remind me of my job.
The Interstellar Wars: Chock full of interesting possibilities, but leave it to SJG. They got dibs on the idea, and I don't want anyone directly competing when it comes to Traveller. This may change if they screw it up, though.
The Rule of Man (The Second Imperium): I'm sure that there are some interesting possibilities that can turned into adventures in this setting, but none have ever really occurred to me. Pass.
The Long Night: Rebuilding an interstellar civilizations from a single planet or cluster? Regaining lost glories and discovering entirely new ones? Exploring new horizons, or finding old ones agains, all while never sure of just what you'll find? Hell, yes!
Milieu 0: Been there, done that, have the crappy books to prove it. Leave it be.
The Civil War: Expansionist neighbors ready to take advantage of even the slightest weakness, while malcontents and political hacks squabble like children over the glories that they've killed their betters for? Sounds good to me.
The Millenium Era (Third Imperium - ca. 1000): The glories of a strong interstellar imperium combined with the potentials of a still (slightly, slowly) expanding frontier. Very interested.
The Golden Age (Third Imperium - ca 1105): The old, traditional favorite. With the bookcases full of previously published material published for this era, some might wonder what's left to cover. All those books are just scratching the surface, the elementary school version, as it were. Now we can get down to expanding on what's already just been touched on, and expand into areas never considered when originally published. Also very interested, but would probably be even more interested in a larger book combining the Millenium Era and the Golden Age (say ca. 950 - 1110), showing how and why the Imperium and its neighbors changed during that period.
The Rebellion Era/Hard Times: Fairly well covered by the MT ruleset, but I wouldn't mind some additional background and adventures, especiallya Rebellion non-Virus alternate history. However, as My Rebellion era TU has diverged pretty far from canon already, I'd place this fairly low on my wish list.
The New Era (Fourth Imperium): I'd probably find this fairly interesting on its own but, as I'd stated above, my Rebellion era TU has diverged a lot, so I'd probably not be able to use much of the setting. However, being the completist that I am, I'd probably get one nonetheless.
An all new campaign setting: Very interested in seeing what might be done, especially if licenses could be arranged to cover David Weber's "Honorverse," the setting presented in his novel "Path of the Fury," or that presented in his and Steve White's BugWar series based on the 'Imperial Stars' tabletop wargame. Lois McMaster Bujold's "Vorkosigan" universe would also be interesting to adventure in. C.J.Cherryh's paired Union/Alliance books would also provide an interesting background for adventuring, although this might be more of a departure than you were thinking of.
Well, you asked for opinions...
Simon Jester