Unfortunately, the world of computer game marketting is far from a certainty. Apart from simply owning the rights, you are talking about many times the cost of them for actually developing the game. I believe FS2 took something like $200K to make, it would most likely be double that nowadays with new technologies and requirements.
Even after development, you need to look at advertising. It's a proven fact that, in the current climate, advertising in computer games has more to do with sales than quality, market studies found direct link between advertising money and profit.
You are probably looking at around $750K to release a game with any kind of clout and with enough exposure to even stand a chance of making that money back. Freespace is not as big a fish as it appears to us ,else why aren't larger companies doing exactly what is suggested here and eyeing up the rights?
Because of the, let's face it, financial failure of Freespace 2, for whatever reason, this has made the whole franchise a touch and go affair, [v] would write it as a 'pet' project, but most other large companies are not going to be all that interested in paying for the rights for a game with an unknown quantity as far as sales are concerned.
The fact is that Freespace, love it though we do, is not that viable a license financially speaking. There's enough programmers out there with their own ideas that it is unlikely that any large company is going to fork out for the rights.