You might find the G46VW with Thunderbolt in other countries (?), but it may not be available in the U.S. or Canada (I'm not aware of it at least).
I don't work in sales though, so you may want to check with more people or try the
U.S./Canadian ASUS support page here to see if they have more information.
Also, you probably know, but when the ASUS website lists the G46VW thunderbolt as optional, it just means ASUS may or may not sell a G46VW version with thunderbolt in your region, but it's not something you add later, etc.
Thanks for your interest in ASUS products and hope this helps you find the answer.