Also, unlike Zelda, Mario, or Pokemon games, Xeno games aren't a surefire success historically. It's not a guarantee best seller or command grabber like the aforementioned titles, so even though XC2 was likely being developed with that knowledge available to Sakurai, there's no predictability to whether a character would be well received from that game or not. He likely would have gone with a character of known renown instead. Moving forward, I would say XC has shown itself to be a safe horse to bet on, and Rex & Pyra will absolutely get represented eventually. But for the base game I think it would have been too early and/or too risky. Maybe I'm overthinking it, but both Xenogears and Xenosaga's franchises were cut short, so who can say until the roster is revealed.