>>26915027Also, Gen 5 didn't have any cause it was supposed to be a 'reboot' to the series and it was the first region set away from the previous 4 regions hence why there were not original Pokemon in B/W until either post game or B2/W2.
Past gen evolutions is still possible but because we haven't seen any revealed yet (and they are what they've usually revealed in the first lot of reveals) they may very well not be any past gen evos, I think they want to make Mega Evolutions take that spot.