We consider Escape Velocity a finished product. We have no plans to update Escape Velocity at this time.
Because of Escape Velocity's open-ended architecture, it is possible to create other universes for the game, as well as new ships, new weapons, new missions, new systems, etc... The possibilities are endless. As a result, Escape Velocity will be fresh for years to come. For more info on plug ins and how to make them, see the question, I want to write my own missions and create my own galaxies; is this possible? for more details.