That's the thing though. Shax, Zavala, Drifter, and Saint WERE the only vendors with ranks prior to 30th anniversary. And all of those reset each season. Xur is the only new vendor with ranks outside of those four. He may work like them and reset each season OR he may not. We don't know and Bungie hasn't clarified.

Gunsmith and destination vendors don’t reset. I would imagine Xur is more like a planetary vendor than a core vendor.

Those don't have the same vendor rankup levels with reset options though. Xur is literally structured exactly like Shax, Zavala, Drifter, and Saint, where every few levels you get items and then at level 17 you reset your vendor rank and start over. Gunsmith and destination vendors you don't have those same rank up tracks with a reset. They're very different. Xur is modeled after Shax, Zavala, Drifter, and Saint which leads me to be concerned that Xur may reset like they do as well. What you're describing is what I'm hoping for. I hope he doesn't reset and is treated more like a planetary/destination vendor without auto-resetting each season. But we don't know for sure yet.