Going by what happened with Twitter -> Mastodon, there were multiple waves. After each wave, things died down a bit as some people who had joined lost interest. But each successive wave brought more people than the last.

I expect we might see something like that here. There are still events to come, e.g. the 3rd party apps shutting down, Reddit supposedly rolling out new mod tools, mods realising they can no longer easily moderate their subreddit, Reddit making further changes like shutting down the old UI, etc. These will all bring refugees, and hopefully Lemmy will be in a better state when they come.