> they will support it only for HTTPS URIs
No. They may do that now but the intention is to support HTTP URIs that force TLS but allow self-signed certificates.
See https://wiki.mozilla.org/Networking/http2
"There is a separate, more experimental, build available that supports HTTP/2 draft-12 for http:// URIs using Alternate-Services (-01) and the "h2-12" profile. Sometimes this is known as opportunistic encryption. This allows HTTP/2 over TLS for http:// URIs in some cases without verification of the SSL certificate. It also allows spdy/3 and spdy/3.1 for http:// URIs using the same mechanism. "