I suspect that Apple are running out the contract with The Weather Channel, and we will see all the tech from Dark Sky fully in the native weather app. I'm thinking it might be an iOSS thing... "We've revamped the stock Weather app with all the cool technology of Dark Sky..."
That would be an excellent situation for Mac users. Especially if they pump some computing resources into improving the daily/hourly forecasts. Guess it will just come down to profits as with everything they do.