Also AFAIK airbnb is not set up for you extending your stay, and other things you can typically negotiate with most hotels. So for various reasons, it doesn't fit the needs of many business travelers (and some leisure travelers).
If there were a brand that was solely targeting leisure travelers, that might be more threatened by airbnb, but that's not how I picture any of Hilton's brands nor any of the brands of most of their major rivals. I would think it's more small forgettable motels that are more threatened by airbnb, but they've been threatened for years by lower-end-but-higher-quality properties anyway. There's a reason that small forgettable motels often have rates that are both a fraction of lower-midscale-and-up hotels and even undercut much of airbnb's offerings.
Hm, maybe Motel 6 is threatened by airbnb?