I like what Stuart has to say here about what to call what we do. Although I think the post pushes the analogy a bit too far toward the end.
Neoclassic is pretty good fit for the whole panoply of what being done with the original rules of D&D. Like the historical neoclassic movement we are not just trying to recreate what was before but doing new things with the material that are fun and interesting.
The fact is that for as many fans of the terms Old School and retro there are as many that dislike them because the words describe a backwards look. The words Classical and Neoclassical to me have a fresher feel to them.
It is worth talking about as words have power. As we grow beyond our initial core groups it helps to think about how the niche wants to present itself to the larger audience. But lest people make a tempest in a teapot, this is a minor issue compared to those involving actually producing products. Ultimately the terms that we will describe what we do will bubble out of the hundreds of interactions between publisher and customers. It messy but it will do the job.