It seems a bit derisory to focus on nostalgia as the sole driving factor. After all, classic film and classic literature still have an audience, even though their origins have passed much further beyond living memory. Why should games be any different?

I think that the technical and artistic constraints under which pre-modern games were created have merit in their own right. It may be less popular once the wave of nostalgia passes, but I expect people will continue to create and play retro and retro-aesthetic games far into the future.