What's Apple's most important product? I'd say that iMessage has a good shout for that title. As I've said in the past it is a key weapon in preventing curious iPhone users from jumping ship to Android.
With rumours re-surfacing of an Android client for iMessage I have to ask: who at Apple thinks this might be a good idea?
The potential upside for Apple is that users get to message their Android owning friends. Doesn't seem like a particularly attractive one if you ask me. That Android interlopers in an iPhone clan automatically become second class citizens by virtue of SMS-only communication is a strong driver for those users to move to an iOS product.
The downsides? You mean aside from opening a hole in the Apple walled garden as an escape route for hard won customers?
If competition from WhatsApp, Snapchat and Facebook Messenger hasn't persuaded Apple to go cross-platform with iMessage (or Facetime) I really doubt that another Google messaging platform is going to be big enough or scary enough to do the trick.