You're not wrong, but that's a very one-sided view. The alternate outcome is that when the current mods abandon ship there's likely going to be many more people waiting in the wings to get their shot at modding their own sub. What other service is a perfect substitute for Reddit? The thought that most users will give up Reddit cold-turkey and stay away permanently is a bit naive. Internet use can be an addiction and addicts staying away under their own power and no alternative is unlikely. Ultimately a vacuum will be created, it will be filled with fresh bodies, and Reddit will continue along after a short period of unrest and uncertainty, with new mods running new subs.
"The time to buy is when there's blood in the streets."
I don't think most users will quit cold turkey. However breaking muscle memory is a really quick way of breaking addictions. If people can no longer use their favorite apps to check Reddit then it'll force them to make a conscious choice to download the official app and relearn their bad habits (assuming they consider using Reddit a bad habit).
If a significant portion of users (especially power users who are more likely to contribute to discussion and posting content) leave the platform then it could cause a lot of issues for the future of Reddit.
new untrained and inexperienced moderators will disrupt the site experience. The poweruse and mod community fleeing to another site will start it becoming more common among barely involved users. Its exactly what happened to digg. The site became (to quote huffman) "profit driven" and it quickly fell from grace.
Could also say it's happened at Twitter, too, outside of sports Twitter. When I had my main account with 2K followers for years engagement was pretty high and consistent. Then Twitter made sharing links to your own content impossible to drive engagement to your own content which, considering the amount of anger and virtue signaling on Twitter, caused me to use it less and less.
Then Elon bought it and it became a right wing platform for what I can only describe as fascism disguised as "free speech". I'd log in and see virtually no one over time. Granted my main account was very tech/developer heavy and those communities seem to skew left. But I decided it just made me sad to login and have to see how hollow it was.
Glad to have experienced it 2014-2016 though. That was peak Tech Twitter for me.
"The time to buy is when there's blood in the streets."