I think JCL will keep the Gamestudio project running with minimal effort as long as some sales still trickle in (like he already seems to be doing since a while) and at some point in the not so distant future it won't be worth it at all anymore.

Then he could open source Gamestudio.

Though it probably would be a lot harder to build a working open source community around Gamestudio (and its parts like the hopelessly outdated editors and a hard to understand Lite-C compiler with chinese comments) than to simply create a Gamestudio clone with already existing and well maintained open source projects like Ogre, Mono, Bullet, a customized Blender 2.6 for level editing,...