Why don't you use B4J ?For desktop solutions I use the mighty but heavy Visual Studio VB which is a good combination with B4A.
Unless you are creating Windows only UI applications then B4J will be better for solutions that work together with other B4X tools. It will allow you to reuse the code and logic and also to reuse the data with features such as B4XSerializator and B4XEncryptions.For desktop solutions I use the mighty but heavy Visual Studio VB which is a good combination with B4A
Even before, when Xamarin was not free, developers who looked for cross-platform tool to build mobile apps and knew C# chose Xamarin, who knew Basic chose B4X. Developers who didn't need cross-platform tool to build mobile apps chose Android Studio + Java, Xcode + Objective C / Swift.I don't think / expect that it will have a large impact on B4X tools. B4X tools are very different than Xamarin. There were always free alternatives (Android Studio + Java, Xcode + Objective C / Swift, Phonegap and others).
Cross platform is an important point. However between 2011 and 2014, B4i was not available and still B4A (then named Basic4android) was used by many developers. Don't forget the RAD (rapid application development) aspects of B4A and the other tools.Developers who didn't need cross-platform tool to build mobile apps chose Android Studio + Java, Xcode + Objective C / Swift.