I refer to Pokémon by their Japanese names untill the games featuring them comes out in English, much like I refer to the regions, characters, and what else there is by their Japanese names untill official English names have been given.
The only instance I've had of knowing the Japanese names was when Black and White came out in Japanese. It was a much discussed topic at the time, and since no English names had been given at the time, I'd have to refer to their Japanese names obviously.
I had a hard time going from Isshu to Unova though, mainly because I liked Isshu much better.