I think a Traveller MMORPG would be rather difficult to pull off, at least as Traveller.
One of the keys to Traveller is that information travels at the speed of travel. This is important to back story, and to real operations. The 1 week jump is central to the game.
But, online, while travel may be limited, I can guarantee you communication won't be. You can't stop it, and people won't sit for it.
I would imagine that in a Sci Fi game, travel between planets is about as involved as travelling between continents in World of Warcraft (which I play), which means it's not involved at all. In WoW you have to go to a boat dock, wait for a boat, get on the boat, travel to the other continent, and hop off. This will take less than 5 minutes. In WoW, this trip is free to take.
I don't know how the other games work.
Now, on top of this 5 minute trip you have to travel to the boat, which means getting to the city. You can either walk, ride a horse, or fly along a preplanned route from another city to get there. If you're in the middle of no where, there are areas in WoW where it will easily take you 30 minutes to get to your destination combined walking, flying, and boat riding times.
Travel is THE largest time sink in WoW. In general, from the player community, Travel is "tolerated". If they had instant travel to anywhere in the world, trust me, no one would walk.
I'm guessing that in terms of "real" space based on walking times, etc, that each of the two continents in WoW are ~25 sq miles in area. The entire "planet" consists of only 50 sq miles of terrain. But, to be fair, that is continguous terrain. If you're suitably strong enough to not get eaten by a Grue, you could walk 60-70% of the surface of WoW, the rest being inaccessible mountains. When you're walking around 50 sq miles is Huge. In Traveller, this is nothing.
This free form ability to "go anywhere" is very powerful. You get a grand sense of exploration and, despite the world being so "small", a sense of freedom and space.
In contrast to something like the game Half Life 2, which was absolutely beautiful, but pretty much constrained you to an area rarely wider than 50 feet (even though you could see farther). You were always on a road, in a hallway, an alley, a river bed, etc that you could not get out of. Very confining.
I don't know how a Sci Fi game works, but as a rule there should simply be no place that I could not go in a Traveller world, unless I'm simply not allowed to purchase a vehicle. I think I'd be unahappy in a Traveller world where I was never able to get out of the Starport, or off the ship.
One of the big problems as a Traveller Ref is keeping the players interested enough to stay on path, or hindered enough to not drift to far off of it. When you have a J2 capable ship, CG lifters, armed, with several weeks of fuel and stores, there's nothing but the players themselves keeping them from lifting off at the LAX Downport and heading out for a weekend camping trip near Kilimanjaro, or if a suitably flat spot can be found, on TOP of Kilimanjaro.
This presents an enormous burden upon the creators of the game. If I want to go to Jewell or Regina, there better be a LOT of cities, with a LOT of things to see and a LOT of people in them to bounce around and off of. That's a HUGE amount of content, and trust me, it gets stale very quickly.
WoW has, roughly, 20 different building types, and they are pretty much everywhere. Seen one, you've seen them all. "Gee this beat up inn in Deathknell looks just like the one in Tarren Mill, Duskwood, and Moonbrook."
Since the games are social, it is important that players can easily get to each easily so they can party up and go on adventures. When you come into the game and find that you're on Jewell while your friend is on Tobia (who just told you that through the in game chat system), you better be able to get together within 15 minutes play time, or there will be grumpy players.
The game needs to be set up so that you can enter and leave at ANY time and not be overly penalized for it. When your system crashes, you ARE leaving the game, no options about it. And typically when you come back in, you should be pretty much able to pop in where you left.
Now, imagine leaving the game mid-jump, and not logging back in for 2 weeks. The game continues without you, and you'll probably reappear either on the ship, or at either end of the destination.
How interested would you be in a game where you could not own vehicles, or if you could, you could not control them. Where trade was done at the broker level, not the operations level. I don't even want to think about what happens if your ship is destroyed in deep space. Typically you need to get your body back somehow.
To me, Traveller is all about scope. Doing intimate, meaningless things (in terms of scope of the larger world) against this HUGE backdrop. Being able to lose your self in any of a zillion worlds across the Imperium.
WoW typically has ~2000 people logged in to a "world" at a time plus the several hundred freindly NPCs and the thousands of monsters to kill and plunder. Imagine the Spinward marches with "only" 2000 people in it . Seems kind of...small..to me.
So, I don't know how a Traveller RPG could be pulled off, since the primary mechanics of the game would really play no role. Can't gearhead, smaller universe, less than lethal combat (there will be a LOT of combat).
I'd want something more intimate than Master of Orion. I'd want a ship I could crew with my friends and land on exotic worlds while at the same time being able to do a breaking and entry scenario on a Labor Union Boss.