honestly I think that opensource is a good mean, and it's not failed at all, in fact you can notice nowadays how many cutting edge project are still being released with OS licenses. But it's a mean, not a goal. The way our world works, OS is not the beast mean for making games and there is little point in trying to make a game that is completely OS just for the sake of it.
This completely random opinion said, because 0AD is open source, it will never die. Anyone can revive it anytime. If there is interest, things will happen. Otherways, they can still happen later on, as long as there is someone that wants to make them happen.