Conservators generally prefer prints not to be drymounted, though of course they will deal with drymounted prints as best they can. The main issue is reversability, and in general, not reversable=not archival by definition. This has nothing to do with questions of whether the mat protects the print or whether drymounting keeps it flat. If, say, the mat develops mold, the print needs to be removed, and it's a heck of a lot easier to unmount a hinge mounted print.
I like the look of a drymounted print, but one sees much less drymounting in the better New York galleries than there used to be. Another issue is storage. Galleries usually have drawers full of unframed, unmounted prints available for browsing.
Flat prints are a passing fashion. We'll all get used to wavy prints eventually. We look at corner mounted prints all the time in galleries and museums and if the prints are otherwise compelling, we often don't notice.
Okay, I'm being a little facetious, but I think the compromise is eventually going to be starch mounting, which is the traditional method of mounting albumen prints. Albumen prints curl more than gelatin prints, because albumen is just less stable, so they really do have to be mounted flat, and virtually all of them are starch mounted, and they've been holding up for about 100-140 years. I haven't tried it yet, but there are instructions in Reilly's book at albumen.stanford.edu. If a starch mounted print ever needs to be unmounted, it can be floated off the board in distilled water.
