While I don’t expect there’s going to be any meaningful impact on Reddit once the dust settles, I do think this will bring a lot of new users to the Fediverse.
Reddit losing a few hundred thousand users is a drop in a bucket given their user base, but it is a significant boost for us.
This is going to work like the Mastodon migrations. It will come in waves as Reddit does more and more shitty stuff.
Most likely, and this works well because it allows time for server capacity to grow and for wrinkles to get ironed out gradually. Fediverse would have a hard time absorbing millions of people all at once, but a gradual trickle of users allows things to grow organically.