I absolutely undestand the wish for a proper Prophet '08 successor, but I find it hard to image how DSI could squeeze that in next to the Prophet-6 and the OB-6.
Mainly for two reasons:
a) A lack of overly innovative aspects from a developer's POV
b) Too many overlaps with other current products and according losses in sales if that would be ignored
The only way I could imagine a successor happening would be if DSI inverted the intention of the original Prophet '08, meaning: If they'd conceptualize an analog poly synth that should not be affordable in the first place, but an instrument that is designed to surpass the Prophet-6 and OB-6 in terms of functionality, polyphony, and price (not from the customer's perspective). Something that would end up in the Modal Electronics 008 range, but maybe with around 10 voices. Not sure how people would respond to something like that though, i.e. how big the market would be.
On the other hand, this would still not solve the problem of a lack of innovation. After all, a bi-timbral Prophet-6 or OB-6 can already be put together by anyone who can afford a keyboard and a module, two keyboards, or two modules. So everything that would be left as an add-on is/are a couple of more modulation slots, and I'm not sure if DSI would sacrifice a whole year of development for something that can essentially be had with other synths they've already released, in particular the Prophet 12 or the Pro 2.