I’d imagine open source is just a small slice of the pie compared to the youtube/twitch/gaming audiences. And I imagine any project earning thousands on Patreon isn’t going to attempt to migrate all of that just to keep it in github.
It will probably only affect Patreon’s share of FOSS-projects starting today (and thus doesn't already have a Patreon).
Of course if enough people start using GitHub Sponsors, end-users may make it a expectation/demand to be able to sponsor their favourite projects there if they are going to bother (much like users today won’t bother to sign up for a Patreon-competitor).
And then it might start having a noticeable effect.
That said, anecdotally speaking, today only one of my Patreon pledges are for software projects, and most are for youtubers.
If that holds up for other people too, I suspect Patreon will be fine.
