The Alpha of Flutter for Windows is out. I think it will be a game changer for two reasons.
Developing for Windows will be easier, Microsoft has let the Windows desktop stagnate from a C#.NET UI perspective, no-one is excited by C# Windows apps. There are fewer tools in the chain to develop on Windows vs mobile. No emulators and app stores to deal with. This will get developers up and running faster. Develop and test on Windows desktop and then build and release on mobile.
Developing in a windowing environment will naturally make the final mobile app experience better. Developers will need to handle and adjust to different window layouts and sizes on Windows (and Mac) and that will translate to mobile, making the mobile experience more responsive to screen size. Perhaps finally some really good Android tablet apps will come out of this.