Yes. We get 2 new materia types every expansion. If you're selling materia, they sell for the highest before the X.1 patch, which we have already passed.

However, they also sell well after major gear-upgrade raids, which is mostly the X.05, X.2 and X.4 patches but also happens from people farming augments in the X.1, X.3 and X.5 patches, although many of those players will get materia from those activities as well.