Given most sites still support HTTP/1.0, it's very unlikely we'll see anyone drop http/1.1 for another three decades, at least. Especially when you factor in how slow some large chunks of the world are to upgrade their OSes and software suites.
Uh, HTTP 1.0 doesn't support the host header, which means that you need unique IP addresses for each host you want to serve.
Ironically, you could solve that problem with IPv6, but...