I think it really depends on how real the 1% rule of the internet is.

TBH I believe that 90% of mobile users uses the official app. Maybe they don’t know about 3PA, or simply just don’t bother. 3PA might be “for power users/advanced users” to them. All they want from Reddit is just the laugh (and porn probably) when doom scrolling. Not to mention because there is an official app, it’ll be the first result when searching “Reddit” on the app/play store. Most of the time people will just go for the first/official one. This whole API/protest thing will just be another Reddit drama for them and they just don’t care.

However, I believe that this whole thing affects those 1% users the most. For mobile users (of the 1%), I believe most of them are using 3PA. As the official is just too bad. For everyone else (of the 1%), if they care (even just a little bit) about Reddit, they will be greatly disappointed with how Reddit handles the whole situation. They will either have left already, or will be leaving soon. Which then the question will be, to where?

Obviously, users tends to go to wherever places that has the most interesting content to them. If enough 1% users left Reddit, migrated to Kbin/Lemmy, and continued to create content over here, I think those 99% users will eventually migrate as well - especially:

1. The content are created by the same 1% users, so the content will be similar to what they consumed back when they were on Reddit.

2. Reddit is full of repost bots, which hopefully should be more obvious when no new contents are being created anymore.

There’s also another possible but quite pessimistic possibility:
Some of those 99% users became the new 1% users, and began creating content with the redesigned UI/official app.
*Puts on tinfoil hat* Which is what Reddit wants - to kick out the “old”, power/advanced users (users who can and will protest/rebel, in essence), making Reddit into another generic social media platform. With everything under the complete control of Reddit, not its users.