They are doing a phased roll-out of the new firmware. It will not appear as "visible" to all serial numbers through the auto-update feature right away. The idea is to let a subset of the owners download the update, then check back with the support lines in a couple days and see if they got calls on it. If all looks good, then they allow all serial numbers to get the auto- update.

As you've discovered, if you're anxious to get the update right away, it's still downloadable.