The 6580 is a supported device, and if you leave it connected to a properly installed comcast cable with signals in normal range it will update when new firmware is available in your area. »mydeviceinfo.comcast.net/stage/d···evid=268
Usually one or more areas may receive firmware updates first as a usability test, however no one will push firmware out of area.
You'll just have to wait until your area is updated.
This is ONE of the MANY disadvantages of All-in-one/gateway devices, one part cannot be updated/replaced on it own.
Contrary to common conspirisy theories modem rental is not a cash cow for comcast or most other CATV/HSI providers, but priced just high enough to be sure it doesn't cost them money.