I doubt this will happen. For one thing, the dominant targets for Linux are servers and embedded systems - both of which are cases where resource overhead is pretty important. Running a Windows to run Linux inside of incurs a pretty substantial overhead, so I really can't see any case where developers would be willing (or even necessarily able) to spare the resources to install Windows on their formerly-Linux-only targets just to maintain the convenience of getting to develop for "Linux" on their Windows PCs.

And desktop apps developed for WSL will simply never be Linux-compatible out of the box at this rate, given that WSL does not contain any graphical or UI functions; MSFT has been pretty clear about this right from the start, and so I really can't see a scenario where people mistakenly believe just developing user-facing applications for WSL will make them "just work" on Linux, given that all the UI code is on the Windows side.