They can change their mind at any time, and I for one hope they do.

Maybe the law is different where you are. In my country, the public statements they have made about ongoing support would carry legal weight, and pulling that support several years early would be obvious grounds for legal action. Potentially they are on the hook for all kinds of nasty things, starting with undermining every consumer purchase of a system with the version of Windows that is no longer supported as promised.

I don't know what you're looking at, but the Google chart I'm looking at for 2010-now shows constant growth, starting at about 2012 and really gaining steam in 2013, and continuing until now, albeit with some stumbling in the first half of 2015. Their stock price now is higher than it ever was in 2013-2014, and is in general going up.

Well, you do know what chart I was looking at, because the link is right there in my last post. Go ahead and follow it, and press the 5Y button.

On that chart, you'll see that after a couple of stagnant years around 2011-2012 that ultimately brought down Ballmer, you can draw a pretty straight line through the stock price through 2013-2014, hitting close to 27, 37, and then 47 at the start of 2013, 2014 and 2015. At close yesterday, nearly six quarters dominated by Windows 10 news later, it stood at a touch over 50, after the most volatile period of trading in years going below 40 and above 55 at times but always some way below the previous levels of growth.

You're correct that the stock price today is higher than it ever was in 2013-2014. What you're glossing over is that it's a mere 1% or so higher than it was at the peak of the 2013-2014 gains, nearly 17 months later. That's not exactly impressive for a business with such a dominant history and supposedly a whole new strategy to recover from the missteps of the previous few years. About the only thing they have going for them lately is that they haven't tanked along with the overall US markets since the start of this year.

Apple's been competing in those markets for decades, and they're still a tiny player.

Which markets? In laptops they seem to have about 10% market share. They're on a comparable scale to any of the big Windows laptop manufacturers, something like 5th or 6th by volume of sales IIRC, presumably higher by revenue since they aim for the top end of the market. That's not nowehere on the desktop for businesses.

The thing is, though, we're talking about 3-4 years out here before Windows 7 runs out of support. If Apple wanted to make a play for the middle part of the market, maybe with a secondary brand, they easily have the financial resources, infrastructure and technical chops to do it.

The other vaguely plausible alternative is that another huge tech firm decides to actually give Linux clients a serious push. Obviously none of the current distros is going to do that; the only one with anything like the resources to make it happen is probably Red Hat, and their focus seems unlikely to shift from the enterprise/server market. But if you look at Android and to some extent Chrome OS and SteamOS, the potential for an unexpected sideways move to some new type of device is always there.

In any case, if the current trend towards outsourced IT and cloud services continues during that time frame, the advantages Microsoft retains in the corporate server room will erode over time, and with them the barriers to migrating to a completely different platform. Obviously it won't happen overnight, but it doesn't have to.