Extremely unlikely. PS3 is the most common console on the market, which means they are being traded and sold more than others. Pretty common netflix box in a lot of households, which requires updates... They move a lot, so buying online is hurting your chances at CFW unless you buy one with it preinstalled or one that's already downgraded. You can get a Slim on ebay w/ CFW for less at the moment.
Though buying a random used console I'd say you'd have about a 60-75% of having 4.82 or lower. Granted you gotta stay away from those 2501 models.