I don't see this being a big deal so long as they have a good number of "Express Lanes" where you can dump your wallet, keys, phone, and cowbell into a tray and walk through. And for the ladies a plastic bag with only the crap you need to make it through the four hours that is the pregame, game, and walk out of the stadium.
And really, who needs to carry a pocketknife all the freaking time? I know, be prepared and all that, but I cannot contemplate a scenario coming up with better than 1000:1 odds where I'll absolutely need a pocketknife during a football game. Better to leave it behind and not get into an argument with security over the length of it.