You sound like you're reading from the RIM playbook circa 2004. It's not a matter of IF, it's a matter of WHEN the product that kills them shows up. The only reason that Facebook hasn't already supplanted them is their horrendous record on security - eventually a player without that track record will come along and eat their lunch. Facebook messenger became "good enough" just about at the exact time the Cambridge Analytica scandal happened - at which point even the non-nerds started deleting their accounts and abandoning their messaging platform.
I think the mistake you’re making is thinking Apple cares about messaging. They don’t. They care about the iOS platform. Messages gives them a competitive advantage in that sector. Yes a competing messaging service might surpass it, in fact this has already happened in China with WeChat. This goes some way to level of the playing field with Android over there.
But putting Messages on Android would level the playing field as well. It might give them the dominant messaging platform, at least outside a China, but so what? There’s no reason for them to care about that. They’re not Facebook.
I think if Apple didn't care about messaging they would just kill their investment and let SMS and 3P apps do the job. They wouldn't just throw money away to make something they didn't care about.
No product is going to come around and kill iMessage because it isn't zero sum. iMessage has a guaranteed priority slot in the OS because Apple owns it. As an Apple user, I prefer iMessage over every other messaging platform. It is just more fun and has better expression. Period. It's too bad I can't iMessage everyone, but hey, I can iMessage lots of people. Don't think that will _ever_ go away.
