I second this feature request. We do a handful of larger ticket programs with limited seats that usually sell out in 10-15 minutes. The ability for an inventory control feature to redirect when all seats are sold would be great. Just like the countdown timer redirects when time expires, once the last spot is sold it could do the same and redirect to a sold out page.
Current workaround is using a ticketing app with inventory control that integrates with OP but everything i've seen charges a portion of the revenue from sales and it is expensive. When done all in OP it requires manual oversight of sales. It is difficult to make necessary redirects without overselling a few spots and having to reach out to customers to tell them they didn't get a spot.