A related development, Imgur is introducing GIFV:
The cornerstone of Project GIFV is a platform-wide upgrade to automatically convert uploaded GIF files on the fly into the MP4 video format. […]
The .GIFV Extension: With all these improvements, Imgur will now denote converted MP4s with a “.gifv” extension. The intention is to signal to users throughout the Internet that these links will feature a GIF experience that incorporates all the current and future enhancements made through Project GIFV. Imgur plans to submit an accompanying specification to relevant standards organizations before the end of the year.