Right and I'm talking about in order for it to be adopted there needs to be compatible equipment. I just disagree with you and think people will adopt it, but it'll take time.
Adoption of height channels can begin any time - not only has Yamaha offered it in proprietary ways for years, but Pro Logic IIz products have been on the market for a while now. Granted, a significant number of those products force you to choose between back surround or height, but the compatible equipment is there. The 978 and 998 will be "compatible equipment" just like the Marantz AV7005, no matter what DAC configuration is used.
People building a dedicated room probably wouldn't think twice about 9.1 or 11.1. In fact, I imagine for each row of seats they'd want a side channel. For those with large format projection screens may want height channels if they don't have acoustically transparent screens. However joe consumer that goes to a big box store and buys a system in a box probably isn't think 9.1 or 11.1. So you're right that the average consumer probably doesn't care, but enthusiasts who put their own systems together will care.
Dedicated rooms are the best candidates, but they are also a small percentage of the total number of home "theaters" even among enthusiasts. In those cases, extra side channels are a different matter - they're going to get a copy of an existing side surround signal - but combining height and back surround channels in one room is more straightforward.
I'm not saying there aren't cases where the extra DAC channels are desirable - there absolutely are such cases out there. It's just that I think it's going to be a somewhat "focused" market.