Hmm, newegg currently only shows 3 camera models that use microsd vs. dozens that use full size, but I can see smaller cameras moving toward micro. Bigger cameras should stay with full size cards since lots of people want to shoot HD video with them. That burns massive amounts of space, so users often want the maximum possible capacity. Lexar just announced a 256GB CF card and they have been shipping 128GB SDXC for about a year. It will be a while before we see micro cards in such capacities, and when that does happen the full sized cards will hold even more.
I do tend to think for most audio users, if 64gb is not enough then no amount is enough, so they will want to use cheap bulk storage (hard drives) rather than flash, and maybe we've reached the era where full size slots in audio players don't matter any more. A big Android tablet is a reasonable HD movie playback device though, and 128gb is just a couple of dozen DVD's, not a big number, so limiting them to micro format seems unnecessarily restrictive.