Interesting indeed. As far as just the domains go, is there any reason that Namecoin could not serve as a wholly alternate domain name system...and not just limited to .bit? If so, perhaps one could make a 'market cap' valuation argument, which would further support the 'backing' notion.
I don't think so. Namecoin doesn't include the suffix, .bit is just a convention. Of course, since it can store arbitrary key value pairs and the key portion has a specifier you could create a new, slightly different DNS that did have suffixes. That would probably cause more confusion than it is worth though.