This isn’t easy to answer for a lot of reasons. People “leave Reddit” in a lot of ways. Some deleted their account. Some nuked all their comments but left the account up. Some just deleted the app. Some stopped using Reddit but will eventually return. Some JOINED Reddit specifically to watch the exodus drama. Some made bot accounts to fuck with the numbers for fun. And of course, some users joined without ever being aware there was drama at all. Looking at the change in the number of users alone won’t yield the answers.
Other useful metrics would be number of posts/comments contributed, and daily active user statistics. But again, engagement may have actually been driven upwards recently because drama is fun to be a part of and redditors are notorious keyboard warriors.
Growth of lemmy and other similar platforms is another metric to use, but that number is affected by the converse of all of the reasons I listed above as well: A lemmy account doesn’t mean they deleted Reddit. It doesn’t mean they’ll stay off it. Not to mention lemmy’s growth is likely inflated by people signing up for multiple instances due to slowdown.
tl;dr: No one is gonna have a good answer to this yet. If they say they do, it’s likely gonna be a pretty inaccurate estimate.