Ok, while this post is based on some not-so-public knowledge, it represents where I personally plant my OTU flag, and not Marc's (or Rob's) or anyone else's positions...
1. I want a set of core rules without a setting, except where necessary for explanations. T5 is close to that. I did try to persuade Marc to drop the "OTU explanation" chapter for more rules space, but lost that discussion.
2. I want some milleu set as a baseline, well defined enough for a newbie referee to play in. 1105 will serve as that, despite a LOT of consideration for moving the timeline forward.
3. I want a solid set of explanations for manipulating that baseline forward and backwards, based on a cleaned up (reimagined is too strong a word) timeline. When I think of how this should work, I'm thinking of a heavily modified version of Jason Kemp's "Alternate Collapse/Recovery System" from Stellar Reaches #5, but able to move forward and backward from 1105 data to 1248 (and beyond) and backwards to Milleu Zero and Interstellar Wars. YMMV. Jason already knows I like his system, and I tried to make Rob and Marc look at it a bit (Ok, I made Marc look at it. I can't drive to Rob's house and do that. Well, perhaps I could, but that would take more than a couple of hours and lunch at Noodles.)
4. For an OTU book for T5, there's some fan material I would want to include. I should probably start a list. Heck, there's some articles from Andy Slack from the old White Dwarf stuff... Some things from the Traveller Chronicles... actually, I'd want open a topic on COTI for people to submit items they liked, and I'd go searching for the author to get permission to edit/modify/update their stuff. I'd want "nothing off limits". The first book needs to have material in it to get a new referee able to build a 3i-feeling game after a good read-through without having an OTU expert at his side.
5. Other supporting material? I miss the days of HIWG, of Tiffany Star and The Imperium Staple, but that's probably not possible given today's copyright laws.
Hmm... too much rambling here.
I do agree with Hans -- I think the possibilities of the Spinward Marches have hardly been touched.
6. I can openly say that T5 will start the timeline moving forward again. I can't say when that will start, but it will happen. And it will include TNE and 1248. Broadly, those items are all canon. Bits here and there might be edited to better fit the 1105 baseline, but "Charted Space" (that's the official name for the official setting of the OTU) will begin moving forward in time again.
7. I'm hoping the OATU (the Official Alternate Traveller Universe) starts moving forward again... It can also benefit from a better fit with the T5 1105 baseline.