With great designs and names they were certainly wasted potential on GameFreak's part. What did you wish GameFreak would have done with them storyline wise?
Actually Anthea and Concordia are in Black 2 and White 2. You can find them in Team Plasma's Safehouse in Driftveil City. They give a little backstory about N but that's about it though.
To be honest I did not notice that they were there until I played Black 2 haha, I managed to completely miss them every time I watched the introduction on my Black. So obviously I couldn't have expected much from them storyline-wise.