Microsoft announces that the company is planning to add support for Android and iOS in .NET 6. The next major version of .NET (i.e. .NET 5.0, currently in Release Candidate 1) is going to be shipped in November 2020, and .NET 6 will be shipped in November 2021 as an LTS (Long Term Support).
If you are an application developer, you should know Microsoft's plan on releasing the next versions of .NET, and the support for Android, iOS platforms. Conversely, they will stop supporting platforms that are no longer relevant.
.NET 5 will be a single product with a uniform set of capabilities and APIs that can be used for Windows desktop apps, cross-platform mobile apps, console apps, cloud services, and websites. .NET 5 is currently under Release Candidate 1, and it will see two more Release Candidates before the final version is made for general availability in November 2020.
Though there won't be any new version of .NET Standard (2.1 being the last released version), .NET 5 and all future versions will continue to support .NET Standard 2.1 and earlier. And you should retarget your applications from .NET Standard to .NET 5 to gain access to more runtime features, language features, and APIs.
Microsoft, in a blog post, said that .NET 6 might add support for other platforms like Android and iOS. You will be able to easily identify the platforms by the name (netX.0-windows, netX.0-android, netX.0-ios). On the other side, Microsoft is going to end support for the platforms that are no longer relevant.
In case you are not aware of the .NET Release Schedule, here it is for your reference: