My guess is that Reddit loses about 5% of traffic by shutting off API access. It isn't great, but it isn't bad either. Spez treats it as a win.
Mod burnout becomes a big thing in a year, with many major subs starting to lock threads and blanket ban harder as the more experienced mods leave and the new set isn't really prepared to handle the workload. A lot of the best of this new block are going to be alt-right, and you'll slowly see subs become more friendly to alt-right views. Mod abuse gets a lot worse.
As the entire site becomes r/conservative, expect the fights that happened with r/The_Donald to be worse and make the site more unusable. This will probably drive off more users as "everything is political". Reddit won't keep its promises on building better mod toolkits, and a lot of LBGT groups leave for other sites.
As the website starts to see a shrinking user base and still hasn't made money, either Spez or a successor goes full Twitter Musk and cuts staff to the bone in hopes of trying to keep some revenue.