Other than the fact that X is more than likely secretly a prequel to this.
I got spoilered on some things that I won't repeat here, but with those certain things and the synopsis of X... Well, I hope some of you can see the logic I'm going with here with how X is probably a prequel in secret.
It'd be a damn dark ending to X though if I'm right.
I'll say it right here. And this has no spoilers, but if they do decide to connect the games, the timeline would most likely happen like:
Xenoblade -> Xenoblade X -> Xenosaga -> Xenogears