Astromechs are cheap to toss out there, so I wouldn't say "never" to any of them making a comeback. I mean, who expected R2-B1 (or whatever he is) from Episode 1, to get an "update" because a better sculpt was out there?
Hasbro's weird like that.
However, I dont' think ALL the astromechs from those sets will ever see the light of day again. Maybe one here and there is all. And to me, they all make good rebel fighter extras. I got extras of most of them one way or another, I think on sale even, and they flesh out a big briefing scene or background street nicely.