You are completely right. That will be true until Linux is proven to have enough utility and be able to run enough the software end users need. Active directory is killer, but there are alternatives.

It's a shame Novell is circling the drain, as it does have the ability to manage Windows and Linux machines in a similar network. If Microsoft fucks up hard enough and the opportunity is there, we might see an exodus. European governments are supposedly pioneering this now.

I'm aware this is still incredibly improbable, but the possibility is growing.