Work just provided me with a new laptop. It was my choice and I selected a new MBP 15 inch. My reasons are longevity - my last MBP, which I own, lasted more than 4 years, and I am still using it. OSX is an excellent operating system. I sometimes go months without rebooting and I use the machine 8+ hours each day. I can also run Windows on my MBP. I prefer VMWare Fusion for my virtual machines but Parallels is fine too.
Had I selected a Windows laptop, I would have only a Windows laptop. Having the MBP allows me to test and develop against both platforms. It also provides me with a way to run the less expensive versions of any commercial software, should there be a difference in cost.
So, while Windows licensing sales may be up, there is no way to know where those OS's are running. Heck, it could be that folks are buying licenses to run on their Macs.