Minecraft won't die. Best selling PC game, second best selling game (tetris is first with about a few hundred million more sales)
Microsoft wouldn't have bought over minecraft/mojang for over 2.5 billion dollars if they thought it would die anytime in the far future.
The only way minecraft will ever die is if people stop playing it. I doubt that will ever happen though, the possibilities with the game are endless.
I do believe the long term future isn't going to be with the java version of the game though. The amount of updates that are regularly coming out are mainly aimed at the windows 10 edition, trying to catch up to the java version.
One of the features of the windows 10 edition which is unavailable in the java version is virtual reality. That's the future of gaming right there.
https://minecraft.net/en/stats/
That's a nice little link to see how minecraft is doing.