A lengthy discussion, beginning on TEI-L:
and moving to TEI-Council:
suggests that it would be a good idea to have a <media> element which could be used in the same way <graphic> is used for images. Other suggestions:
@mimeType should be obligatory
@medium should be obligatory, with values including video, audio etc.
The element should remain simple, like <graphic> (which might now be seen as syntactic sugar for it), and not venture into the complexities of similar HTML5 elements