I understand why we can't but I do miss playing with my PS3 friends. I may have to plug the PS3 back in at some point just to catch up with them again. At least we still can exchange messages through the PSN network.
I am loosing one of my valued clan members to the PS4, but the good thing is that he will now be able to recruit some PS4 members into the clan. I agree that eventually one will have to migrate to the 4.