Each time Google re-ups their #GetTheMessage campaign, trying to shame Apple into doing the thing that is objectively best for everyone (supporting the open, federated messaging system everyone else uses alongside thiers), I think a little more about Apple's side of things.
Here's what I think will eventually happen:
Apple makes an Android iMessage client, makes it free for anyone also using it on an Apple device or paying for an Apple service, makes it act as an SMS client too, and users just set it as default SMS client.
Then, when reporters ask Tim Cook when he's going to stop making texting their grandma be awful, he can say "you should buy your grandma an iMessage gift card," and it'll be significantly less stupid and snarky, and people will do it.