I'm pretty sure most redditors won't care enough to leave. I predict the only people actually leaving will be old guard (like 35+) and FOSS nerds who pine for the good old days of the internet and/or otherwise have ideological qualms with the changes. Everyone else will just grumble and get the ad infested, inferior official app.

Even if they reneged on everything, I still wouldn't go back. The problem with Reddit at this point is the quality of its users. It's next to impossible to find any kind of legitimate discussion because everything is buried under reddit-comedy and virtue signaling. Most of the major subreddits have just become political tools for their mods. It scares me thinking how curated the posts are there.