What will the timeline backdrop be for this 5th edition? Marc has mentioned the year 200 of the Third Imperium, the time of the Julian wars. That would put the action trailing of the Imperium... but there was once another vision for M:200.
Looking back at T4, we find that some ideas for M:200 were already in the early planning stages. Here is a quote from Stu Dollar's What If? musings:
Milieu 200. The Traveller that might have been as interesting as the other Milieu. This would have also been the first study of a non-Imperial centered backdrop for Traveller other than TNE ever. Centered around the Aslan Border Wars with the various Solomani pocket empires, including the Earth Union, Milieu 200 would see no Imperial presence. I do remember something else distinctive about what we wanted to do with Milieu 200. It would have scrapped the black bordered cover of T4's books to date by going with a field gray. We envisioned gray, with royal blue lettering, to make the books more eye catching, and distinctive from Milieu 0. As I recall the suggestion was well received, but the general impression was that it would be a year or more from GenCon '97 before Milieu 200. But anyways, here were the suggestions for the first rollout of Milieu 200:
This companion adventure to Milieu 200 will be released simultaneously with that volume. It consists of a linked group of adventures detailing the struggles between the various Aslan clans and the small, pre-Imperial Solomani governments in the area. The emphasis is on diplomatic and espionage missions, rather than straight military campaigns. Twin campaigns are included, one of which is from the Solomani point of view, the other from the point of view of the Aslan.
[Dark Nebula has always been one of my favorite campaign settings. The Keith Brothers did some pioneering work on the sector, but there were so many interesting things about the blend of cultures here that we felt that more could be done].
This is the next step in the unfolding story of the Third Imperium, to be released at GenCon '98. This volume provides all the details necessary for running a campaign in the years 200 to 400 of the Third Imperium, Aslan Hierate, or the Solomani Pocket Empires. Milieu 200 includes sector data, and maps, historical essays, important world write-ups for the Solomani Rim, Dark Nebula Sector, and surrounding areas.
The Starlane is a series of linked adventures, and further campaign hooks. The setting is a tenous trade route known as the Starlane, which links the growing Third Imperium with the worlds of the Earth Union, Easter Concord, and other Solomani governments prior to Imperial integration. The adventures focus on piracy suppression, trade, and exploration.