Well, the single voice version of the Prophet 12 is already there along with some more bells and whistles: the PRO 2.
Other than that, it'll be likely that we'll see a monophonic version of the Prophet-6 under the Sequential banner. As for desktop modules: I'm currently wondering whether it wouldn't be more economical for DSI/Sequential to develop more Eurorack modules instead of desktop modules. First of all because the Eurorack market grew significantly ever since DSI started business, secondly because even Roland and Moog are now into it. And there are still some elements of their flagship synths that would make sense as a module: The digital oscillators of the Prophet 12/PRO 2 for example and/or the new VCOs of the Prophet-6.
The prices in Europe fell after the prices were cut in the US. I think, though, that it affected more than just these instruments, so it might also have to do with the fact that the Euro is getting stronger again, dunno. But then, the prices of the Prophet '08 keyboard and desktop module, the Mopho x4, and the Prophet 12 module have been lowered as well in the US, and those won't be discontinued (yet).