Yes, they will continue to update Minecraft. As you may have noticed, almost every Thursday they release a snapshot, which is sort of like a pre-release of the next update that they will add to the game.
Minecraft will continue to get updated until a time when Minecraft isn't so popular. Then the development of Minecraft might be given to the community.
I said this. Two days later, my computer's motherboard melted down and I had to get a new one with Windows 8.
Irony in the first degree.