Due to the popularity of Flash and its native ability to deliver rich media content, there were thousands and thousands of hours of eLearning courses developed to be played in Flash Player.
Flash was a king in delivering the online content before the Mobile era. But as soon as the smart phones started gaining popularity, Flash started to take the back seat. Although, during the initial stage of Mobile era Flash Player was supported in most of the Mobile OS. But when Apple stopped the Flash Player support in its iOS devices due to performance issue, the usage of Flash started to drain in Mobile devices. Apple clearly declared that Flash is not suitable for low power devices and multi touch interfaces.
Please read more on Thoughts on Flash from Apple CEO Steve Jobs.
At one hand, the popularity of Flash Player started to go down and on the other hand the HTML5 started to gain popularity & it is replacing the Flash Player slowly. The main advantage of HTML5 is that it gets rendered in any browser irrespective of device and platform and moreover it does not require any plug-ins to be installed in browser. This feature gives the flexibility of developing one website for both Mobile and Desktop browsers and the HTML5 content gets rendered based on the target device dimension.
Although, Adobe has stopped further released of Flash Player. But it is actively engaged with HTML5 tools. Adobe has already launched tools like Adobe Edge Animate which is similar to Flash IDE but creates HTML5 content on publish. One can recreate the existing Flash files to HTML5 content using Adobe Edge by means of Sprite Sheets.
Also, there is option in Adobe Flash CC as well to convert the Flash content to HTML5.
HTML5 has become one of the dominant way to deliver content in modern browsers. It has taken an edge compared to all other methods as it is independent of plug-ins.