And do you think we will see young Rickard Stark, Olenna, Tywin, Jon Arryn etc in Dunk and Egg?

Eh…dunno. Jon Arryn was born between 218-220, Olenna born in 228, Rickard Stark was born sometime after 230, Tywin was born in 242. 

The most recent Dunk and Egg story was set in 211. So that’s a long time for those characters to be born and then grow up sufficiently to appear in the stories as actual characters.