I'm not nearly as pessimistic about a blanket ban on lead. For one thing, it wouldn't hurt "just" hunters. You drop down below the 20ga, and steel shot simply doesn't make sense even for skeet shooting. So you'd be scratching 2 of the 4 "official" gauges in competitive skeet, the .410 and the 28. There's also a fair amount of small bore sporting clays going on now, and that makes even less sense than steel for skeet.
But with modern steel technology--especially improved shot cups--I think the issue remains more one of pressure than it does the steel pellets themselves, when you're talking damage to vintage guns. Assuming, that is, relatively open chokes. But the small bore guys would really be hurting, and of course the days of cheap plinking with a .22 would be over as well.
And I think the DNR's will get around to looking at the other side of the nontox issue, which is what it would do to hunter/shooter numbers. Their budgets rely on license sales, and on income from the PR tax on firearms and ammunition. Fewer licenses sold plus less revenue from firearms and ammo sale = less money going into DNR coffers. And they can do a lot more for the environment and wildlife with the money they'd lose than whatever gains would be seen from a lead ban.
