I guess we will never know the true longevity of Minecraft as a brand. It will be too easy to dismiss any future decline on Microsoft's handling of the brand.
I was on the side of people who believed that Minecraft was here to stay, and even with little manipulation of the product, it would still be around in 5 years. Now I am not so sure. I think a massive company like MS handling it can only harm it. I can easily see conent updates being walled off as DLC or a completely new title.
How soon until we seen a major Minecraft spin off or a completely unnecessary Minecraft 2 release? 2 years tops? Maybe even sooner with XB1 struggling. I bet they will continue to "support" Minecraft on all platforms, but major changes and updates are going to quickly become exclusive on MS platforms. I don't think this buy out is a good thing for the game if you haven't noticed, however, well done to Notch, what an insane payday. Well deserved, Minecraft is probably the most important video game since Mario.