File format has to my knowledge nothing to do with long-term survive-ability of video files. As a matter of fact I vaguely remember reading somewhere that every time a video file gets re-encoded you will lose some information.
As long as the internet will last there will most likely always be access to codecs for the playback of any old file formats.
As for batch conversion, people usually mention Handbrake which seems to be one of the best converters around: https://handbrake.fr
The cats are watching us...