I would say the reason of having two lines of macbook: air and pro is because of technology constraint before. The only advantage Macbook Air has is lighter, but compromise of performance. Now, Apple can make powerful laptop for similar weight. I would say the mission of Macbook Air is accomplished and time to retire. It makes sense to focus on one line of Macbook where it is light and powerful. It is good for customers as there is no confusion of choosing whether to get a pro or not, now you just need to choose what size fits your purpose.