Work on HTML5 was completed several months ago, but the new standard is seeing slow adoption around the Internet, despite possessing significant advantages over other standards such as Flash. Twitch has started the long process of switching to HTML5, but it is going to take some time before the site is completely running on the new standard.
As Twitch begins the shift to HTML5, the company plans to temporarily implement a hybrid HTML5 and Flash system. The video interface will be in HTML5, but the underlying video itself will still be in Flash. This is a necessary step, as an HTML5 player is developed for Twitch. It is hard to say what benefits, if any, this will have in the immediate future, but eventually the plan is to be completely using HTML5, and when that happens things will significantly improve.
The biggest advantages HTML5 offers to websites is the increased security and decreased bandwidth required for features that have traditionally been driven by Adobe Flash. Through the use of an API layer, companies can apply a number of DRM and other security technologies that allow the content owners to control their uploaded content, and prevent that content from being illegally downloaded.
At the same time, HTML5 has support for Google's VP9 codec, which uses an encoding scheme that requires less bandwidth. When YouTube made the switch to HTML5 back in January, it was reported that VP9 was able to reduce the necessary bandwidth for transmitting a video by an average of 35 percent. In addition, with the use of MediaSource extensions and Adaptive Bitrate (ABR), the content can be adjusted as needed to use less bandwidth, and ultimately can reduce buffering by over 50 percent (or up to 80 percent on some networks).
These dramatic reductions in bandwidth demands result in less strain on the servers streaming the content. This means that the current servers will be able to handle a larger number of requests before being limited by bandwidth, and the time between server upgrades can be extended. On the user side of things, this results in less buffering, allowing you to view your content faster.