I don’t see Old Reddit lasting long. They’ve cut beloved features before, and they’re still calling New Reddit a “beta feature”. After they’ve pumped enough resources into developing it, I’m sure they’ll move past the “test” phase and just cut Old Reddit out entirely. That’s probably going to be Lemmy’s next big user surge.
Does Reddit suppress mentioning Lemmy? I remember for a while this past June 2023 there were a lot of auto-deletions for mentioning or linking to Lemmy. I was never clear on who was deleting things and where. I guess linking to the r/Lemmy subreddit (or a fediverse sub) could work as long as the subreddit doesn’t get banned.
Honestly, I don’t think users would migrate from Reddit to lemmy if they shut down old.reddit.
At this point, and after all that happened, users would switch to the new Reddit and continue using it.
Reddit has a massive amount of users and content there is generated at a huge amount. A lot of users would continue using Reddit even if they aren’t happy with the interface, just for the content really.