So its all in the details.
Apple are removing the Dark Skys app from the Playstore, it will no longer be available to download. The website will also cease to support anything beyond "support of API and iOS App customers" apparently.
iGP does not rely on the APP, but use API calls to get data directly from Dark Skys. This will continue to function till end of 2021. So regardless of your OS, (android, iOS, windows) the weather will continue to work.
From what I can see the only impact is for anyone not on iOS, without an API key you wont be able to access any weather data beyond the small amount of data the iGP app provides.
Full blog is here
https://blog.darksky.net/