Yes, Http2 is supported. See the WildFly 9 CR1 release notes: https://developer.jboss.org/wiki/WildFly900CR1ReleaseNotes
HTTP/2 & SPDY Support
Undertow, the web server in WildFly has added support for the new HTTP/2 standard. HTTP/2 reduces latency by compressing headers and multiplexing many streams over the same TCP connection. It also supports the ability for a server to push resources to the client before it has requested them, leading to faster page loads. We also include support for SPDY, the predecessor to HTTP/2, in order to support clients that have not yet updated to the new specification. Although, currently, recent versions of Chrome and Firefox provide support for the standard out of the box.
Note that using HTTP/2 requires using Java 8 with a specialized setup procedure. This is because the HTTP/2 standard requires a TLS stack that supports ALPN, and a stock Java install does not include support for it. The extra setup steps will go away once Java 9 is released, which is expected to include ALPN support. Since HTTP/2 is also a goal for Java EE8, it is also expected to be made available in a future Java SE 8 update, likely after Java 9 is released.
It can be added as following:
/core-service=management/security-realm=https/authentication=truststore:add(keystore-path=server.truststore, keystore-password=password, keystore-relative-to=jboss.server.config.dir)
/core-service=management/security-realm=https/server-identity=ssl:add(keystore-path=server.keystore, keystore-password=password, keystore-relative-to=jboss.server.config.dir)
/subsystem=undertow/server=default-server/https-listener=https:add(socket-binding=https, security-realm=https, enable-http2=true)