A traveller EDITION needs design sequences. The OGL T20PH is just that, a "Player's Handbook for T20," not a new "Edition of Traveller."
Releasing an edition without any design sequences is not going to improve things. Releasing one with poorly done, or worse, dangerously over-detailed and yet still poorly done ones (FF&S2 comes to mind).
Sci-Fi games without some form of design sequences are fairly rare. The long-running fan-base ones, Traveller, Space Opera, Space Master, and Star Frontiers all had design sequences. Most editions of Trek RPG's had design sequences (Notable exceptions: Starships and Spacemen, and LUG-Trek). Most of the larger Generic engines have some form of design system: GURPS has G:V, Hero includes rules in the core, CORPS has VDS, EABA includes them in the core.
SW-D6 (WEG) has a modification system.
Car Wars new edition has left players without a design system; most of the AADA chapters seem to have stuck with the older materials, with design systems.
Dream Pod 9's games don't have a "Design" system, but do have an "Evaluation and Rating" system that gives context to the designs and tells if they fit the general level of the setting.
Having a design system, at least for ships and vehicles, is a good thing. Having it in the "Player's Manual" probably isn't for most games.