We saw this before with Alien Blue, which was previously the top iOS app. Reddit bought it, promised to turn it into their official app, killed it, and released a version with fewer features and more bugs.
If Reddit buys Apollo, there's zero chance they let it operate independently. Christian gets a nice payout and all his users leave for the next best option. If I'm reddit I don't think I see that as being worth the cost that the app's userbase might be on paper just based on API cost.