Can't help but wonder if it might not be time to start a FOSS alternative just in case Anki begins to decline.

It might not be the worst idea to do that anyway. Anki is great, but there's plenty of room for improvement. Off the top of my head, an architecture that doesn't involve fragile and finicky python bits and is designed to support multiple independent clients would be a nice step up (Telegram is a good model here — make a core lib with all the nuts and bolts which devs build clients around).