What concerns me most about Apple's future is they are losing market influence. The 80% Android number does matter for this reason.
Say a brick and mortar store decides to adopt some kind of smartphone payment system. Are they going to choose Google Wallet or Apple Passbook?
Wallet works on Android and iOS, Passbook only works on iOS. Passbook's market penetration peaks at ~16%, whereas Wallet's penetration can reach ~95%. This type of influence allows Google to shape the mobile market, in the same way Microsoft shaped the PC market.
If I'm a shop owner, I can serve both Android and iOS users by adopting Wallet, so why bother with the expense of also supporting Passbook? This will _eventually_ cause developers to not bother with iOS, and then iOS will become MacOS of the mid 90's.
Apple will need to either start to tightly integrate Google services into iOS, or they will need to open their services so they can be ran on Android. And that later approach would be extraordinarily tough, because they'd be fighting Google on Google's own turf.