Flash platform has no native, built-in DRM (apart from RTMPE which is not native to the Flash platform but comes from Adobe), if JS interpreters could catch up with AVM2 performance to handle heavy encryption, byte manipulation and connectivity you could write your own DRM-like system in HTML/JS as well. That of course won't happen soon...

Flash is not going anywhere but not because of DRM, but because it outperforms HTML5/JS combo in all the important aspects, both feature and speed wise, except for the video HW acceleration (in selected browsers, that is), which is precisely why Adobe is investing so much resources to bring HW video acceleration to as much platforms as possible.