I know that information is limited for Pokemon X/ Y. I also know that there has not been a game trilogy since gen4. If a 3rd game came out for sixth gen, would it likely be "Pokemon Z" or would it be like gen5 and have Pokemon X/Y 2?
It is very possible that there will be a trilogy again. But this was also said about black and white and there were rumours of there being a Pokémon grey due to Kyurem looking like a a good trio-master. This was never the case though. As much as it looks possible we can't really tell since this is all GAME FREAK's decision. Personally I do think that there will be a trilogy this time and maybe a few remakes, but this is just a matter of opinion