I've never been a fan of using <link> for connecting to every sort of
external entity, since it makes it impossible to write general purpose
<link> handling code (for unknown @rel values) without ending up doing
things that degrade the user experience. But that battle has already
been lost (when the idea of reserving <link> for links intended for
traversal was rejected).
The question now is, what benefit do we get in exchange for
implementations having to be updated to look for the images in a new
location? If there's no concrete benefit, I'd vote for keeping it as
it is. It'll be simpler for new implementers if they don't have to
discover that something in the spec has been deprecated. And it'll be
simpler for everyone if there are fewer ways to do the same thing.