A couple of years ago, Carsten Dominik posted a message on the RefTeX
newsgroup asking whether people were switching from bibtex to amsrefs.
If so, he said he would consider implementing amsrefs parsing in
RefTeX. I gather that he didn't get enough response (or enough time) to
warrant doing this. Now that RefTeX has become part of the AUCTeX
project, I wonder if the maintainers have any plans to implement amsrefs
parsing. I switched from bibtex to amsrefs several years ago, and I
maintain parallel bibtex and amsrefs files so that I can use RefTeX.
This is do-able, but it would obviously be more convenient if RefTeX
could deal directly with amsrefs files.