I have auto update turned off for apps, so I didn't get the last update for Infinity and I can still use it to see Reddit, for now. Once it dies I'm out though. I can't imagine they will be able to get enough subscriptions to support the app, so I'm not really sure what the goal is here.
Even the people subbed to r/Infinity_For_Reddit are saying they won't buy a subscription. Wouldn't Infinity be racking up a huge bill from Reddit once the API change goes into effect? There's no way subscriptions will cover that so I don't understand why they're doing this.