From the looks of this, the technical version of what this means is that Netflix has been working closely with Apple to bring MPEG-DASH Media Stream Extensions to Safari (they're already present in Chrome and IE11), and that MSE will be in the Yosemite release of Safari. This is good news for MPEG-DASH adoption. Hopefully we'll also start seeing hardware H.265/HEVC support in new silicon soon which will really open up the door for 4K (and significantly reducing current bandwidth usage for 2K/HD)
Contrary to widely held popular belief (especially among marketing types), there's not such thing as "HTML5 Video". There's a Video tag in HTML5 that allows you to embed a video player in a web page, but there's no standard as to what that actually means. When someone says they "support HTML5 streaming", they're spewing you a line of BS, because it doesn't exist. There are currently at least 5 different ways to send video to an HTML5-compliant browser: Apple HLS (supported by Safari, some WebKit browsers), MPEG-DASH (Supported by IE11 and very recent versions of Chrome), RTMP (Supported by Flash), RTSP (Supported by all kinds of things, but no adaptive streaming), and progressive download (Supported by just about anything, but can't do live streaming). Silverlight is HTTP-based, but not supported directly in the browser (Microsoft missed a golden opportunity with IE10+ to do that), and Adobe also has an HTTP transport called HDS, but it's not useful outside of Flash.
Once you've figured that much out, then you have to figure out what codecs your browser supports. If you're trying to stream live to Firefox, your options are pretty much Flash or nothing, since it supports neither HLS, DASH, or H.264, although MSE is being developed into the Firefox code, it's not ready yet - https://wiki.mozilla.org/Platform/MediaSourceExtensions
And if you're running Android, all bets are off depending on Google's whims for that particular version's stock browser. When Android 4.1 came out they took HLS support OUT of the Android browser and at the same time got rid of Flash support, which means that in-browser streaming on Android became limited to the ancient RTSP protocol (HLS is still supported in the OS media player, and can also be accessed via API). Chrome for Android sort of supports MSE for DASH, but not yet. Google isn't part of DASH-IF, so they're not exactly anxious to support it on Android.