One of the reasons I heard about not opening the tomb is China lacks the knowledge on how to best preserve the artifacts. And they want to leave it for future generations when such technology / knowledge may be available.
Surely by now, China will already have the know-how. Not to mention this can be a fantastic money spinner in terms of tourism and also showcase the might of the ancient Chinese Emperors to the Ang Moh world.
Does anyone know of any other reason why this is still not excavated yet?