Facebook is nowhere near as dead as you think it is. It is still the best place for local groups and many niche hobbyist groups. I really don't want reddit to be another version of that, 1 crappy social site is enough. Also you're missing a key differentiating factor: facebook has actual paid content moderators.
I don't think reddit will die, at least not right away (remember, digg shut down finally in 2018).
Best case scenario is they hemorrhage users, fail ipo, and then join the fediverse. I say this because joining will create a bridge for new users to come here.
Worst case scenario is they become like twitter. which is possible.
My money is on them trying to sell to Microsoft or Google for ai training, and keeping their api private.