Given the AT&T One X was updated 4 months after release and the AT&T GS3 was 5 months after release, I think us AT&T users can expect a prompt update.
This is completely wrong. One X came out in April 12.
Jelly Bean wasn't out for the One X until March 2013 . That's almost a year.
http://www.cnet.com/8301-17918_1-57573133-85/at-t-rolling-out-jelly-bean-to-htc-one-x/
S3 launched in late June 2013. AT&T pushed the update to all of us in December
http://www.androidcentral.com/att-galaxy-s3-jelly-bean-update-hitting-kies
Samsung is faster than HTC by a good amount. Plus this time around, Sammy is releasing the phone with the newest version of Android, until HTC.
HTC seems to have one of the worst track records (down there with LG, etc). Instead of pushing out JB to the One X in the Fall (like they should have), they just released a whole new upgraded model (One X+)HTC is one of the better (actually the best overall at 4.8 months) as far as OEMs go in updating their phones - while AT&T ranks third as far as carriers go (6 months average time).