I've been thinking about this before, but more in the sense of ever-increasing copy protection: I would propose that, in order to qualify for extended-term copyright, an unencumbered version is put in escrow, outside of the copyright owner's control. This would then ensure that when the copyright term is over, the work is still available and in a suitable format for adaptation.

Not sure how that would translate to MMO games though... should we put only the code and design in escrow, or also (parts of) the generated worlds? Player characters? Design tools?