>>52809780I did the list myself if any is wondering. Only 7 pokemon have appeared in both gens since the beginning:
Tsareena
Mudsdale
Salazzle
Mimikyu
Toxapex
Oranguru
Passimian
Counting isle of armor we also have Palossand and Lycanroc.
I believe Mimikyu is going to be a mainstay, together with the fetichized waifus