No one knows if or when they will start spawning again. Some spawning pairs that are moved can take years to get back in the groove - even when in a dedicated tank with perfect conditions. The only thing you can do is feed them heavily, keep them undisturbed, and maintain excellent water conditions. You didn't tell us anything about your setup, but if they are in a dedicated tank, you might consider dither fish. I am assuming they have a nice place to lay their eggs (like a terracotta pot, large shell, or something similar?)