In 1995, the process began for HTTP to be replaced by a ground up redesign. The HTTP-NG project went on for several years and failed. I have zero confidence that a ground up protocol that completely replaces major features of the existing protocol used by millions of sites and would require substantial application level changes (e.g. switching from cookies to some other mechanism) would a) get through a standards committee in 10 years and b) get implemented and deployed in a reasonable fashion.
We're far into 'worse is better' territory now. Technical masterpieces are the enemy of the good. It's unlikely HTTP is going to be replaced with a radical redesign anymore than TCP/IP is going to be replaced.
Reading PHK's writings, his big problem with HTTP/2 seems to be that it is not friendly to HTTP routers. So, a consortium of people just approved a protocol that does not address the needs of one's major passion, http routers, and a major design change is desired to support this use case.
I think the only way HTTP is going to be changed in that way is if it is disrupted by some totally new paradigm, that comes from a new application platform/ecosystem, and not as an evolution of the Web. For example, perhaps some kind of Tor/FreeNet style system.