I didn't load my OTA right away as I was about to commute when I received it. When I checked the system update page in settings after I received it, it said "via WiFi only until Oct. 4." This suggests to me that it will be pushed OTA via mobile network after October 4. What's the alternative? They pull it and you're SOL?
EDIT: Also, I know for a fact I got 4.0.4 over LTE because I was at my parent's house, where they have 25Mbps on LTE, so I don't bother connecting to their crappy Comcast 10Mbps. Granted, that was only 34MB and this one is, IIRC, 145MB. So that may have been a factor.