Well, a fanbase is driven by the shows usually, so without new shows, not much new product will be developed. Macross Zero so far only has 1 toy in development, and multiple models have been released.
A toy developer has to have some reason to think creating a new product will be profitable, so it makes sense that things are slow now, though I'm surprised no Macross Zero toys have come out yet to test the waters.
Hopefully a new TV series or OAV will be announced soon, otherwise, Macross product development will keep slowing.