I skimmed through The New Testament Documents as promised, and it does not appear that Bruce comments on dates for I/II Peter and I/II/III John. He does accept the Pastorals as genuine Paul, so that would place then pre-70. I imagine @Jay was going largely off that linked chart. Its not clear what their methodology was, but form the fact that they only list pre-70 dates for I/II Peter, I imagine they reject any dating that relies of pseudography out-of-hand.

Really, none of the answers do a good job defending either the conservative view or the critical view (Dick states it accurately enough, but doesn't defend it). The linked Wikipedia blurb, although described as "excellent" is quite poor, mixing different views randomly without citation or any apparent reasoning. It is worse than any of our answers (it might have been better in 2013 when it was linked). ... It seems clear that I am going to have to write my own answer. :)

@ThaddeusB Sounds like a good approach :)

Here's a great one from Mike that didn't get near enough attention that it deserved:

That's why I gave it a bounty 8 months ago.

@fredsbend Nice. Really, both answers are quite good, though I like Mike's use of sources. I wonder if there is more to tease out from the proto-Reformers and Reformers though...

Never mind, I see the accepted answer now. All around a nice group of answers.