You talk about interoperability as an important thing...sure, it's important on some levels. Having said that, it's hard to convince the stakeholders that they can't get the product they want because our homogenized MS environment supports it fine, but we're concerned that we wont be able to run it if we potentially decided to switch to Linux in an undetermined amount of time. I'm sure that would go over REAL well. Obviously you're correct about smartphones and tablets being game changers. The difference between the mobile revolution and the Linux/Apple revolution is....wait for it....the mobile revolution actually happened. I don't care how much you like Linux or Apple, their market share in the enterprise is miniscule.
Let me explain this from another standpoint. Having a web site that works with whatever browser doesn't mean that I'm anxiously waiting for Linux or Apple to take over the world. I don't believe Linux is going to take over the enterprise desktop any time soon if at all, anyway.
But I don't know what's coming down the pike in IT. Just 7 years ago I don't think anybody but Steve Jobs would have truly known how much folks would be hitting web sites from phones and tablets now. Even Windows has had dramatic changes from version to version.
We're in a position now where almost everybody who still uses IE6 does so because they have some shitty software at their company that requires it. Think about that. "Interoperability" doesn't just mean "Mac, Linux, Windows, whatever". It also means "Windows XP, Windows Vista, Windows 7, etc.". This is key: even if you're just going to stick with Microsoft interoperability is just as important. People stuck on IE6 now are using a browser that isn't even safe to use on the internet and doesn't work well with modern sites, anyway.
I've also found that folks who write code that works just about anywhere also tend to write code that also works "later".
So, yeah, this stuff is important. I have to think about it a lot in my business, and I help others think about it, too.