I'm not raising points about TNE to start flamewars, I'm just pointing out that Traveller IS still alive today, and that's all that really matters, no?
(oh, and Joe, you'd be wrong about me there - I got into Traveller just before MT came out, I bought some LBBs from a friend of mine at school. I liked MT, really liked the DGP material, and loved the TNE material. T4 just didn't appeal to me one bit so I skipped that. I like GT for the detail it goes into, and I think the T20 material is pretty good too. So the timing doesn't really come into it, I just like TNE because I like that sort of thing

).
But anyway... I earlier pointed out a list of the top 5 companies and their market share, so that gives you some picture of what the market is like.
But Traveller isn't really high on people's radar. It seems to be a pretty closed community - a few new people are trickling in via GT and especially T20, but it seems to appeal largely to the same old crowd who were always into it, rather than the "core gaming market" which is in the 15-30 age bracket.
Although probably not all that reliable, I started some surveys here about how old people are compared to what game they first got into, and the people whose first experience with Traveller was with T20 and the people who first started with CT are in the same age bracket - 31-45 years old (with a strong peak between 36-40). That age bracket is not the core market that RPGs are aimed at (Which is more like 15-30). So that indicates that either the same people are buying Traveller that always have done (given the amount of "collectors" here who like to buy everything ever written for Traveller, this wouldn't surprise me at all), or that Traveller just appeals to the tail end of the RPG market, which in itself is much smaller than the core.
In other words, I think Traveller is doing well enough to support itself, but it isn't getting the core RPG market excited about it anymore.
Why not? Could be any number of reasons. Bad reputation could be one reason (the first thing people I talk to say when I mention Traveller is "yuk, isn't that the one where people die in character generation?" or "that's the one that old guys play, right"?, even though this isn't true anymore). Changing tastes of the RPG market is most certainly another - roleplaying "average joes" in any setting has always appealed to only a small portion of the market anyway. Most people just want to "kick butt and take names" in a heroic manner. There's nothing wrong with that, but one has to accept it as the way things are - otherwise D&D wouldn't be so popular, since that is primarily aimed at exactly that group of people. Exalted is another very popular game, where people play demigods in a chinese-action-movie-fantasy setting - again, because it appeals to the "cinematic", high action, high heroism crowd. These games are popular for a reason, and it's not because their fans have no taste as some people here would undoubtedly say

.
Ideally, it'd be nice to attract people to Traveller again in their droves. I don't think the current tropes of a CT-like setting will do that, unless perhaps it's touted as "Firefly, the roleplaying game". Certainly, that TV series got a fairly big following before it was cancelled, and there are probably a significant number of people who would love to play in a setting like that - but there's arguably too much baggage from the OTU to really pull it off and get the same feel, without changing things a lot.
Another thing is that there are other games around that do it better. CT was touted as a generic scifi RPG game, but now we have things like GURPS Space and Star Hero and D20 Future to do things like that, and they're specifically engineered for that purpose, and to be current in the modern market. There isn't really much interest nowadays in using in a "generic" background that limits the GM to certain assumptions (no biotech, no nanotech, jump drive takes a week and is limited up to 6 pc etc), which is what CT does (FF&S rectified this by providing a lot more options, but that was associated with a less popular version of the game).
That's what I've seen anyway, by keeping my ear on the ground at places like rpgnet where industry pros do show up to talk about such things. We just had some very lengthy discussions about why Traveller isn't more popular, and how to make it more so - but always the problem boiled down to the fact that the existing Traveller community was very reluctant to see the necessary changes to the game that would make it that much more popular. And if there's that much inertia there against change and evolution, then Traveller simply won't be able attract new people in large numbers. TNE was a step in that direction, but it was probably
too big a step, and ended up causing a lot of friction in the community (which still lasts today) - but that doesn't make it wrong to try to change and adapt to the current mores of the market.
It would seem that Traveller has enough fans to sustain it, so long as it stays pretty much as it is. Personally I think it's better for it to evolve if it's to become competitive in today's market.