1000 issues were already created. The issue #1 ((ID=1) was created on 2018-06-16. The issue #1000 (ID=1064) was created on 2018-09-19. So an average speed is 1000/96 = 10.4 (issues/day). An information about these created issues is shown here.
P.S. Some issues are not real problems because there are users who think that moderation queue is some kind of game. For example, there is a case when one user reported that other user was vandal, but this other user had 0 changesets and 0 map note actions.