Watch him get to England and swing the ball and win us a game against India or dare I say pick up a few early scalps in the semi final/final...?
I am still hopeful, regardless of his action or decrease in speed (still bowling around that 138-141kph range) I feel he is an incredibly intelligent bowler irrespective of the fact that he is getting swing or not. Even in the current PSL, his economy rate has been pretty good and bowled some good spells.
In addition to that we have seen bowlers like Shinwari (bowling at even 150kph) be extremely expensive. So it is definitely not all about speed. When Amir was given the new ball for the Karachi Kings, I saw a couple early deliveries show some shape in. (watch opening spell to Kamran Akmal - Peshawar Zalmi)
Take him for the England series, and watch him there, that will answer all of your questions, period.
He is a match winner on his day, has the temperament to deliver under pressure which I feel will be crucial in the world cup. All these other names, hasnain, rauf, musa, might be great raw talent but to be a world cup winner you need big match composure which for them is still a work in progress. Amir has seen it all. He is going to be essential in Pakistan's world cup winning chances, should he get elected and you can take that to the bank!