You're confusing trademarks and copyrights. Trademarks are specially registered "identifiers" -- 'Wing Commander' and 'Privateer' are trademarked because those are how the games are uniquely identified. That prevents other people from making an unrelated video game called Wing Commander or Privateer, even though they're common words.
Trademarks don't apply to all the internal intellectual property stuff -- ships, characters, concepts, etc. Those fall under copyrights, which EA will hold by default for the next 80 years or so. There will never be a situation in our lifetime (and there likely will never be a situation at all) in which a major copywrite lapses in the manner you're looking for.
Well, there's several differences... but mainly, the idea for having a line of novels came from pre-Electronic Arts Origin, who sought out a book packager. Baen didn't decide it wanted to have Wing Commander novels and called up Electronic Arts, it was the other way around.