If I am correct, the only concrete sign of collaboration between Mamiya and Phase is the release of some slightly discounted packages including a Mamiya 645AFII and the Phase backs.
I don't really see what else these 2 competitors would be doing together... Mamiya has clearly shown with the ZD that they know how to collaborate with a chip maker to produce something very decent at an extremely competitive price.
Their know-how is based on Dalsa technology. The logical evolution would be for Mamiya to release soon a new version of the ZD/back using the 33MP version of the Dalsa chip. This could be done with zero modification to the physical bodies and would only require enhanced processing potentially with 14 or 16 bits.
That's clearly what I would do if I were them.
Regards,
Bernard