If Cilan travels with Ash, i don't cilan to catch Fennekin. Fennekin is the only new starter whose design i actually like and it would be a waste with Cilan. On the other hand, Ash does not need an evolved fire type or an evolved grass type.
I wish Ash could bring both Gible and Pikachu with him to the new region and not catch the regional bird and grass starter for once. But sadly it is not going to happen