With an even smaller sample size of my 14 year old from time to time he grows up to more grown up games, but he keeps coming back to Minecraft. He loves the hackability aspect (setting up servers, installing plugins etc..) to it that you don't get from these other games. Now that he is starting to learn to code I am hoping he will start developing plugins as well.

If MS can nurture the hackers and enable them to create and maybe even monetize their hacks, then it should be possible to keep a core set of fans well into adulthood.