Ah, so you be happy having a copy of the Mona Lisa and trashing the original painting? As we've seen since the beginning of the digital revolution, raw digital captures keep getting better and better because of the advances of raw processing capability. No having access to the original would really be a big problem for archivists.
Realistically, most images that reach the hands of archivists are probably going to be in a final output format like JPEG, or worse yet, prints that must be scanned, rather than any kind of raw format. So archivists would be relatively thrilled to get images in a format like 16-bit TIFF without the lossy compression and 8-bit per channel limitations of JPEG. (Or in any raw format for which they know the specifications.)
As a practical matter, I think Erik Kaffehr has a good strategic idea in this post in a related thread
. My version: only buy a camera if and when it either uses an acceptable format or good software is available that supports its raw file format including lossless conversion into a suitable format. Note that this rules out things like formats with encrypted white balance information that third party software cannot reliably read.
(Aside: I would not compare a TIFF to a human-made copy of a painting. A large, high quality print made under the control of the photographer is a closer analogy, assuming that the photographer is in control of the conversion to TIFF, even if that just means choosing the settings on the camera.)