It would be neat to show the patrons what the approximate wait time is for an item if they place it on hold today. It would take the due date + the number of days it can wait on the hold shelf + the number of days it can check out for x the number of people on hold queue and say when you could (in theory) expect it to arrive back in library.
*** Bug 29947 has been marked as a duplicate of this bug. ***
There is a lot that might influence this... local holds priority, renewals allowed if more items available, ...