10% Kanto , 20% Johto , 5% Hoenn and 65% 4th gen.
10% for Kanto because it is the original.
20% for Johto because we miss them since G/S/C.
5% for Hoenn because we actually see them in R/S/E.
65% for 4th gen because its a 4th gen game!,
I really get bored of Magikarp, Zubat and Tentacool but I think having them in this games is unfortunately inevitable. Pikachu will be in these games too but fortunately it isn't as common as zubat and tentacool. I fear that wingull, poochiena and zigzagoon will be common in these games but I hope that it won't because each generations have their rattata ( sentret, zigzagoon,~poochiena) and pidgey(goot-hoot, taillow, ~wingull).