I agree with dragon, lead isn't going anywhere it is just hard to find it free or nearly free like people talk about being the case 10-20 years ago. If you look up the historical commodity value of lead it increased greatly in the 2000's along with a lot of other metals, I think this got a lot of people's head in the game of "hey this is worth something" and now hardly anyone gives it away for free as a result. Lots more people "doing scrap," or at least aware of scrap value, than there used to be I believe.
Lead wheeel weights are still the standard in most states and I think that fact alone means we won't have too much trouble sourcing supply (albeit having to buy online) for decades to come. Until/unless it becomes highly scarce for an oddball reason (gov't bans etc) I think you'll see lead commonly sold online in ingot form for 1-1.5 times its scrap value shipped, just like it is now. When the price goes up, more people sell off some of their horde, so it tends to even out I think.