With the caveat that I'm not an expert in the subject matter, I have found this document well-written and easy to read. I believe it is ready to move forward.

A minor nit, in the IANA considerations section:

| In addition to the actions below, IANA should terminate the Link
|   Relation Application Data Registry, as it has not been used, and
|   future use is not anticipated.

I believe this rather important requirement for IANA is somewhat lost in the different sections. It should probably have it's own 4.x section.

Thanks

Carlos