I think the reasoning works in both directions. I have seen very few instances of companies partnering like that to develop new products. The closest I can come is OPPO's work with NuForce to refine the analog audio design of OPPO's players, and that was much different in scope and focus. I just come back to asking why McIntosh would want to partner with such a radically different company (different target markets, different price range, and different distribution channels) for a project.

The MX-136 is a few years old, and the feature set reflects that. There were many receivers and a few processors from that time period that did HDMI video only. The Model 990's use of DVI mainly served as a good way to be clear with consumers that they weren't getting audio. The MX-136 did offer some video processing that included transcoding of analog video to HDMI output, which was less common. As for replacing the MX-136, McIntosh already has an HDMI v1.3 product available (the MX-150), which leaves them with even less reason to want to partner with anyone to develop something. As intriguing an idea as it is, I just can't figure out a way in which it would happen.