That's probably a little ambitious. In the past 10 seasons, only six rookies have averaged 12 points and 8 rebounds: Yao Ming, Amare Stoudemire, Emeka Okafor, Blake Griffin, DeMarcus Cousins, and Brook Lopez. Two of those guys averaged at least 14 and 9 (Griffin and Okafor).
Among this year's rookie class (admittedly a weak one), only one player averaged 13.0+ points (Kyrie Irving), and none averaged 8.0+ rebounds.
I was understandably ambitious but I feel he would be very productive with the spacing the Cs offense would give him. In college, high school and AAU he has been constantly double and triple teamed. His strength and post game is going to look alot better with room to operate and this past season he showed much improved range on his jump shot.