I believe it is declining rapidly. For example, the Fraenkel Galllery in SF, which is as upscale as West Coast galleries get, recently showed work by Katy Grannan. Her older prints were Type C & the newer ones archival pigment prints - with no apologies for the latter.
Henry Wilhelm established some time ago that pigment prints on good paper now outlast Type C, so any gallery that has sold Type C should not be shy of inkjet.
A quote from the NY Times article of June 5 on print permanence:
"Mr. Reilly and Mr. Wilhelm agree that a big leap for inkjet printing came with the development of inks whose coloring agents are pigments, which are suspended particles, rather than chemical dyes. Mr. Wilhelm says his tests have shown that pigment inkjet printers from several makers now offer better longevity than conventional color prints."