if there was another 150 pokemon will they be mostly fairy types?

Something makes me feel like they are not done re-typing Pokémon yet. There will most likely be some more fairy-types, but, I have to agree with what's been said above. They're probably not going to be mostly Fairy-types. When they introduced Dark and Steel, there were only 8 new Pokémon with those types, not including retypes (Included, it would be 10). Since then, they have been getting additions, but not as many as some think they should have. There probably won't be too many Fairy types to start off. Since the Dex is going to be divided into 3 sections, I assume old Pokémon, maybe even some old legendaries like Mewtwo (the new form), will return. I would say Eevee, to introduce Sylveon, but Eevee wasn't in Sinnoh during the main story until Platinum. Neither were many, if any at all, of the other Pokémon with new evolutions.