If it was the end, they would have made a big deal about it when it was first released.
It would be:
"X and Y...the final chapter in the epic Pokémon saga!!"
Not:
"X and Y coming in October!" 5 months later: "Oh by the way these are the last games."
And if there's a third game or remakes or sequels or prequels or anything else in gen 6, I still won't think it's the end. There is no reason to end something that is so commercially and critically successful.
It's also the turning point in the art style, and the first time we're seeing international releases. It promises big change, so it would be awkward to end it at gen 6.