It's like 2015 is going to be remembered as the year when Apple set in motion for its in-house developed chips to replace Intel chips in Macs. This started with Apple using a relatively underpowered, by today's standard, Intel chip in the new Macbook as the much anticipated iPad Pro wait in the wings to be introduced with an updated iOS 9 more suitable for power users. And this iPad Pro will sport a brand new A-series chip with comparable computing power but a longer battery life than the Macbook.
In fact, the iPad, since the very first iPad introduced by Steve Jobs, have a longer battery life than most of the Macbook variants including this 12" Macbook.
One can assume, then, that Apple will allow this new Macbook battle it out on the market with the iPad Pro.
More at On Apple.