And I have seen this switch in myself as well. I only got into this hobby in 2013, where most of the prints I bought in 2013 and early 2014 were primarily from Mondo. There has been a huge switch since though, and I have been buying more fine art and originals from artists I was introduced by Mondo and you fine folks.
So I imagine that is what is happening. These guys are just moving on, out to try and do other things. It might be that you may never see another print from these guys through Mondo ever again. But that's the cool thing about Mondo, they are always looking for new amazing artists to add to their lineup. That's what I look forward to.

EDIT: I wrote this semi longish post and just realized everyone before me is pretty much saying the same thing. Just adding to that thought I suppose!