The first somewhat working version of the VLC plug-in is available now: GitHub - ue4plugins/VlcMedia: Media Framework plug-in using the Video LAN Codec (libvlc).
It should play H.264. I haven’t tested rtsp:// yet, but http:// works. This plug-in still has a lot of issues and is not finished yet (subtitles and audio are missing, etc). I do not recommend using it in production yet, but if you want to mess around with it, please do not hesitate to send pull requests 
Please note that VlcMedia includes pre-compiled VideoLAN binaries that are licensed under LGPL. It is important that you consider the implications of this when distributing your game. Check the repository’s readme file details, and definitely also check out the LGPL license in the /ThirdParty/vlc directory.