Well someone's got to code it
Commercial software and open source are a bit more linked than most would like to admit. They are generally the same developers.
Windows is not pirated as much as say Photoshop, or MS Office. The CAD stuff probably gets a bit of a hammering as well.
Really, I think most developers hope the commercial field in unix will open up for the medium and small enterprise. The home user is a bit of a sacrifice in getting to that ground. No one codes the big business applications without wondering where the money will come from. Open source is useful to a degree but only to developers and those wishing to wade through the code. I think most users equate open source with free as in zero cost to them to install, the source code is just not accessible even though it is open.
Drivers, development tools, hard to configure network tools, those will always be open - interesting to see what happens to the cash cow projects of knowledge systems that some people rather foolishly tried to make open source. Quite a lot of those you don't hear about anymore, and where is the advantage in looking after those unless you have a support contract setup.
So, personally I am rather looking forward to more commercial apps but on the unix platform, so if MS would just start to think of moving over to unix and ditch their OS, which by now most be more of an Albatross around their necks and come join the party I think that would be great.