I still think the answer is "nobody knows." In theory, it may be possible, but there would seem to be specific cases where it is almost certain that it will not be possible.

DVI/HDMI compatibility is be different than what we can expect to see with HDMI v1.3/v1.4 compatibility. After all, HDMI was based on DVI, and up until recently the video signals that one used were also supported by the other. The issue with 3D is that they are adding video signal formats that neither DVI nor HDMI v1.3 included. From a simple wiring standpoint, it wouldn't matter. It's when those signal formats get processed by a device in the signal path that things may get messy. Unlike the Model 990's DVI switching, many HDMI v1.3-based products actually process the video signal. That video processing is often an integral part of the video signal path, and it is built specifically to support the existing video formats we are all used to. Even now, some units have limitations with those existing formats. In some cases, they can't pass 1080p/24 through from a BD player to the display. I can think of at least one Faroudja-based receiver that converts 1080p to 1080i even if the output resolution is set to 1080p. Receivers like that would probably not be able to pass 3D content. It's like taking a 768p display and feeding it a 1080p signal - unless it has a video processor that knows what to do with that signal, all you're going to get is a blank screen or a message that it is receiving an unsupported signal.

The other concern is video bandwidth. The DVI switching in the 990 has enough bandwidth for the needs that existed prior to 3D. Will that switching start to have problems when you increase the video signal bandwidth requirements for 3D? Will the same be true for HDMI-based products that were designed to the same requirements? How will we know? At this point, I don't think anyone on the consumer side has those answers.