It's not that they're one judgment away from that day. They know that. It's just that they want to get as much mileage as they can before they too abandon Safari and first allow, then switch to Chromium. That will happen in the next 5 years.
What might come of it all would be a reset where new branches form and new innovators get to introduce new proposals. Standards aren't a bad thing if they're open. If Safari dies then Google will be next in the line of fire for antitrust action anyway... things will fragment again. I'm personally pissed at the number of great technologies left as litter along the road, not least AS3, just to get to this shitty middle ground / cold browser war between two companies I hope die and one that won't help itself. Let the standards win and let's have a standard platform to innovate on top of.
I'm not a great future-reader myself, but I don't see this happening soon. The web is a great threat to their app (and also subscription) revenue stream, and they have a lot to lose with little to win for their platform. They lag behind because they want to, not because they can't.
This is as ridiculous today as it has been every year since the iPhone began.
Mobile web apps are terrible and despite all the years of promises that "feature X" will fix this nothing has changed. And you can't blame Apple because Google et al could easily have made mobile web apps work on Android.
If you want to make a mobile web app then go right ahead. Apple isn't stopping you. But just don't be surprised when no user is interested in it.