Mine was gotten at Best Buy two days after Black Friday, so of course I had to upgrade to 4.2.1 unless mine had been speed shipped and just arrived in store that day,
LOL.
It is just time line of inventory and shipping dates from China to Apple or certified Apple resellers like best buy it really does not matter if you have to upgrade or not. This is no different from buying any computer or printer or software applications as in most cases they are out of date when you purchase
You can tell by the picture of the Home screen on the front of the box, if it has the game center icon then it's updated to 4.2 if not it's older version