That is a clever answer. Not to say that Pakistan can not absorb 3 million people back, but here is some back of the envelope calculations.
Now Saudis can not throw out every one overnight as it will cause their GDP to suffer. They will have to replace them over an extended period of time with local workers for mundane jobs. Very high skilled jobs as well as for wage slaves, will be replaced by other foreign workers. But this all takes time.
In this event, Pakistan will see its unemployment rate to go up by perhaps three percent if all these 3 million return to Pakistan, due to the frictional unemployment and as per Okun's law Pakistan will have to increase its GDP by 6% to absorb them all. This would be about, 14 billion dollars increase in current GDP of Pakistan.
To do this, Pakistan will need a few billion dollars in investment as well as solving the energy crisis in order for industries increase their output and jack up the GDP. China can help with investment part. They are sitting on a 4 trillion dollar foreign reserves. And you know who can help Pakistan to overcome energy demands
.
As they say. Every problem has a solution.