How would that happen, exactly? Particularly with the GPL. If an author (company or otherwise) distributes their work, they're required to also provide the source for that work.
Thus, no author distributes their GPL'd software with an expectation that they will make a profit by keeping others from using that code.
So whether the main project continues to use their code or replaces it with other code of comparable functionality is irrelevant. In fact, most entities who buy into Linux do so (in part) to offload the maintenance expenses associated with that code base. So if the community picks it up, win. If the community does not, you 'break even' as you're in the same position of maintaining the code base internally as you would would have been if you'd not open sourced it in the first place.
