Nginx 1.9.5 brings built-in HTTP/2.0 support, replaces SPDY

Nginx 1.9.5 will ship this month shipped 9/22 with new HTTP/2.0 support:
http://nginx.org/en/docs/http/ngx_http_v2_module.html

It replaces the SPDY module since they cannot be both active at the same time. HTTP/2.0 spec was finalized May 14th 2015 so it can now be implemented and standardized.

HTTP/2.0 features only work over HTTPS (tls/ssl) connections in most browsers which is unfortunate since virtually all WordPress based websites could benefit from the speedup.

There is a catch in that your server must use OpenSSL 1.0.2 or newer (or be backported with ALPN support ala Redhat)

Nginx must be compiled with

./configure --with-http_v2_module (etc.)

and then in your Server {} block replace spdy with http2

server {
    listen 443 ssl http2;

This demo claims to demonstrate how HTTP/2.0 is faster for many small elements on a page:
http://www.http2demo.io/

Firefox 36+, Chrome 40+ and IE11 (on Windows 10) currently support HTTP/2.0 over TLS
https://en.wikipedia.org/wiki/HTTP/2#Browser_support