Just tried and found out that:I hope it works as you described last.
a) Pokémon without evolutions are stuck with the foreign name forever, even after mega-evolving.
b) Pokémon that evolve are stuck with the foreign name even after evolution, at least that was the case for Glumanda which evolved into charmeleon but retain its name Glumanda. Now I don't know if this is because my game is in english, and it just recognized Glumanda as a nickname, so a German game may still have a chance to change Glumanda to Glutexo (Charmeleon) once it evolves.
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