It's not just with Denim. I had this issue with my Canadian-sourced unlocked 520. It was on Black for the longest time until Rogers in Canada released Cyan then it got updated. It was still months later before the US 520s, finally got the Cyan. Now I have bought an RM-985 sold by msoft USA, yet I still have to wait until AT&T get off their collective lazy asses and roll out the full Denim. Then msoft will roll out the RM-985 version too.
Dumb-assed way of promoting the Windows Phone - msoft. I don't want to go back to google-data-theft, but it sure looks like I may have made a dumb decision stay with WP by getting the 830. A PlusTwo may be on my horizon.