Yes you do need Windows. Wine is great, but there's no way I'll publicly release a windows application that hasn't been tested on an actual windows install.
Microsoft gives virtual images of their OS for free for development. You can work on any platform and test on VMs.
You can cross-compile from other OSes using MinGW and test via the free Windows VMs that Microsoft distributes. You can also download the free Windows development VMs and develop from them exclusively.