According to Kotaku, the creators of Minecraft are planning on porting the game to Android and iOS in house. This would, supposedly, include both mobile and tablet versions. Questions remain as to how the interface will be reworked and how resource-intensive it will be. Perhaps this will push for better optimization of the game, sooner?
Minecraft is still in beta (having just been released from alpha at the end of last year) and may possibly remain in beta by the time a mobile variant arrives.