Late to the party, but I'm among the naysayers. I don't know about season long pitch counts because that only affects a couple years of a players career. But, game pitch counts probably take 15-30 wins off a pitchers career. That's just a guess, but how many pitchers get up to 110-120 pitches by the end of the 6th, get taken out to see their lead blown?
Another big reason players will never get to 300 again is because of injuries and money. Players get shut down all the time now if teams are out of contention for minor injuries. I'm sure that happened a little in the past but not to the extent we see today.
Maybe it could happen but I'm doubtful and I agree that 250 is going to be the new 300 for HOF standards. Maddux, Johnson and Glavine, maybe Clemens will be elected and then a pitcher won't get in for awhile except for the closers. Once Santana and other guys who had long careers but didn't make it to 300 the committee will have to reevaluate. Guys like Mussina, Pedro and Pettite will stir up the debate and probably won't get in. Once they get to Santana and whoever else had great careers despite not getting to 300 they'll have to change the rules. It is written.