Going out on a real limb there, given that they're already worthless. I can't imagine that there'll still be "circulating coins" 30 years from now. They're already a niche, and by that time, equipment to handle electronic payment will be cheaper than a heavy metal box with a slot on its side.
Probably nothing, unless it's a $50 piece made of copper-nickel clad that you can use in a vending machine. By then inflation will have made the dollar the new half cent. I think that nothing would be the better guess. It will all be electronic and on computers.
Possibly small denomination coins we have today will be replaced with physically small coins of higher denomination.
I would like to see in 31 years that we eliminate the dime, nickel, and penny. After 2% inflation annual for 3 decades, I'd imagine there'd be very little use. How about only our bills, 50 cent pieces, and quarters for our currency.
There’s a good reason for Paddyman’s suggestion. We have had trolls come on here, starting thread after thread, in an apparent attempt to cover the lead-in directory page. CU had one of those a couple of weeks ago and basically succeeded — until they deleted the posts and banned him. Asking questions for your kids is cool.
I'd be surprised if currency is still used in 2050. They want to track everything and the push is already on to use cards for their convenience. It will cut a lot of jobs once we go fully cashless and changeless.