Herb has already said that there will be an extension to Dimension Brass, and Dietz has often mentioned future plans for MIR, so they are not entirely secretive. I'd love to know what else is being planned long term. Perhaps Dimension Woodwinds?
I found the idea of the Low Brass section in Dim Brass and interesting departure. I wonder if continuing the development of non-unison Dimension instruments has potential, although it would be surprising if VSL took the idea much further -it's not Symphobia after all [;)]