I think the dominance that Windows had over the years is finally closing to an end. The Netbook era that is dominantly distributed with Linux is slowly grooming new Linux users, and as these Netbook users graduate to Notebook and Desktop usage at home or office, they surely will opt for using Linux.
Companies will also follow suit in using what their users are confortible using. It won't just happen over night but it surely is happening. This revolution will force MS to be more competent and we may start seeing reduced pricing and more user friendly releases.
I see Linux making a huge difference and Windows regardless of their dominance and financial power will bow.
I honsetly doubt this will happen. Yes, there will be a steady chipping away as the competing OS's grow more user friendly and slick, but unless Microsoft truly stuffs up, Windows won't lose its dominating spot at the top for years to come.
Companies are not going to follow suit as you put it, there are not enough technicians to handle that kind of load. That is why companies standardize on a specific platform. Also, in the USA, they have some very strict compliance acts that require desktop computers to be very locked down. While I'm sure it can be done with Linux, the ability to use Group Policies in a Windows domain really makes things easier.
I like Linux, and I think it has its place in the computing world, but as a replacement desktop for Joe Soap, that's still a way off. Accountants and other people just want to click Pastel Partner/Payroll, and have it run and run well. I'm not sure if there is an equivalent powerful package on Linux, and I don't know how well they would work under Wine.
Above all else, Linux will need to clean up its file system hierachy. /usr/bin, /usr/lib/exec etc isn't very user friendly. Vista for example has Program Files, which makes sense to most people who look at it, as does Windows and Users (aka Documents and Settings) Clean, simple and logical.
Just my 2c
