The WinUI 3.0 alpha will be for testing and feedback and fairly rough. After the alpha is out, Microsoft is planning to get the full Win UI 3 Xaml platform migrated over to GitHub in open source form. A more complete preview of WinUI 3.0 is coming in the first half of 2020, according to the team's roadmap, and the final release of WinUI 3.0 will happen sometime next year, as well.
The WinUI 3.0 alpha will start with UWP. Among the features not yet implemented will be WebView. Credit for all this information goes to enterprise software developer Ginny Caughey (@gcaughey on Twitter), who has tweeted a thread with an update on WinUI 3.0 today, October 30. Developers will be able to create new WinUI apps using the new Visual Studio 2019 project templates. For existing UWP Xaml apps, "there will be some updates required when migrating to WinUI 3.0," however, Microsoft is acknowledging.
WinUI 3.0 will result in the full Windows 10 native UI platform being fully decoupled from the UWP software development kit. This means users who want to build new Windows apps will have a choice of using Win32 or UWP and .NET Core or C++. Microsoft also will be enabling other frameworks like React Native when running on Windows. Developers who are still interested in "modernizing" their existing Win32 apps with the Windows 10 UI can do so at their own pace using the latest version of Xaml Islands, the roadmap notes.
Microsoft plans to ultimately replace WinUI 2 with WinUI 3. Microsoft is telling developers the existing UWP Xaml programming interfaces that ship as part of the OS will no longer receive new feature updates as part of the move to WinUI 3.0; instead, they will receive security updates and critical fixes only. The roadmap notes that "all-new Xaml features will just be developed and ship as part of WinUI instead."
Microsoft has a significant number of developer-focused sessions on the Ignite docket, which is unusual given the show's traditional history as an IT pro-focused event. One of the most anticipated sessions next week is "Windows App Development Roadmap: Making Sense of WinUI, UWP, Win32, .NET." Several attendees are hoping they will hear more about Microsoft's vision toward bridging the UWP/Win32 divide there.