One of the recent novels - Out of the Darkness - actually contained a preface that has some relevance for Elite Dangerous, too. What I got out of it is that interstellar travel was slow even with jump drives, and pilots had to use "stardreamer" capsules (a reference to the time lapse feature in previous Elite games) to place themselves in hibernation. That's how it worked for hundreds of years, and the various ships we see in the game are old because they were so successful and robust, leading to those names building up a reputation the corporations likely were unwilling to risk with newer products when they didn't offer much improvement. Instead, successful designs would see their lifetimes prolonged by newer series building on top of that reputation, such as with the Cobra Mark III or the newest iteration of the Viper.
Also, we've got to remember that those ships are, in effect, mostly just hulls (and thus just an exercise in geometry), with their interiors receiving a lot more upgrades and updates over the decades than the outsides. Another novel - Wanted - features the Fer de Lance, which is said to be a design over a hundred years old, but still called "the best heavy interceptor ever built" by pilots. However, as the FdL's owner in the novel points out, her ship has been completely refurbished from the inside, and modernised to state of the art specs.
Anyways, the setting most recently saw a huge technological breakthrough with the commercial release of the Frameshift Drive, which allows ships to create an energy density field of negative mass and travel via spatial contraction at speeds far greater than that of light. Suddenly, entire systems could be crossed in mere minutes when it took days or weeks before! And the kicker is, the FSD works in hyperspace as well, cutting down jumps between systems to mere seconds. This is the start of Elite Dangerous: where a whole new generation of pilots is suddenly faced with the ability to travel across the
galaxy, a prospect that was considered unthinkable for their forefathers who had "only" normal hyperdrives. Thus, as David Braben once mentioned in an interview, we now have an entirely new "gold rush" where humanity pushes outward, far beyond the frontiers settled during the previous "gold rushes" (first sublight deep space exploration, first hyperdrive invented, ...).
I'm sure other scientific advancements were made as well, but mostly on the fields of optimisation and miniaturisation rather than conjuring breakthroughs out of thin air. This is just part interpretation, part personal preference, however, as I feel that a technologically stagnant setting is "grittier" than one where thousands of worlds all invent new tech every week. We should also keep in mind how the two greatest power blocks in human colonised space - the Terran Federation and the Empire of Achenar - are not exactly focused on constant scientific advancement. The Federation's culture revolves around media and entertainment, keeping the populace happy and docile, whereas the Empire consists of people who either participate in a galactic contest of "who is the most decadent", or are serving them as slaves.
Considering how, in mankind's history, scientific advancement seems mostly driven not by enlightenment but rather military need, perhaps it just took the Cold War between the Federation and the Empire or the Thargoid War to promote interest in funding R&D .. after several centuries of humanity just d**ing around in space believing they were all alone. Ironically, that's the only reason we actually stood a chance against the Thargoids at all, who have travelled through space far longer than mankind - but, very much like ancient China, at some point just stopped advancing and stagnated, allowing the human newcomers to catch up.
Speaking of China, perhaps this helps understand how a culture can just "stop" advancing, and that the setting in Elite is thus quite possible:
http://en.wikipedia.org/wiki/Histor...China#Scientific_and_technological_stagnation