This guy kills 270 people. It was not a youthful indiscretion. It was a planned and deliberate act of terrorism. He fully understood the nature and consequences of his act. He was sentenced to life in prison. His life is not yet over.
So, why would anyone think Al-Megrahi should gent any "compassionate leave" to get out of prison to die, just because he is diagnosed with terminal cancer? What message that send to other terrorists? Wouldn't it be better to let the other terrorists in the world wonder if he will be buried with pigs (and thus not attain paradise for his martyrdom)?
My grandmother lived about 35 years after her diagnosis predicting 3 to 6 months to live. That could happen here, couldn't it?