That is my prediction as well. It's unfortunate as we'll enter the unindexed web where all that helpful content you can find by appending "reddit" onto any search will no longer be getting produced. All of it hidden in discords, out of sight.
Who knows, maybe there will be an easy way to get stuff published out to the proper web. Things like community FAQs or guides that would be broadly of use. I think the loss of the conversations about minutiae will just be a fact though if that migration happens.
Discord is "where information goes to die", so for that reason I think there's relatively little risk of lock-in from discord. The history there might as well not exist, so there's less reason to stick around instead of jumping to a new platform when discord is inevitably enshittened.
I do wish discord were federated. That's my main gripe with discord, it's not federated and I can't bring my own client like I could on IRC. Oh well, with luck the enshittification will happen soon to put people into the mood for trying something new. Advocating for something like Matrix to discord users now is hopeless, just pissing into the wind. I've tried it, but nobody cares about problems they might have with discord in the future when it's working fine today.
The content being out of sight also makes discord communities harder to grow.
I bet that a considerable fraction of Reddit users became users by googling something and finding an interesting Reddit discussion about the topic in the first results of Google.
Honestly, email lists are better than Discord in a lot of ways. There are standard ways to make them indexable via Google, you can use whatever app you want to, threads are a first class feature most people use, and since it's so open filtering can be very powerful. Bots are also extremely easy to write since basically every programming language has the ability to send email (and usually also to receive it via at least one email server protocol which isn't controlled by the distribution list, but by the bot writer).
