I'd buy it instantly, when it receives a 14 inch brother.
I really don't understand why the screens are becoming smaller and smaller with Apple, while the phones get bigger and bigger.
A 12 inch screen (or 13 inch on the Pro) just isn't big enough for watching a netflix video with two persons, or doing reading stuff the whole day, or just browsing the web in full glory.
And since the macbook pro 15" is full of specs I really don't need (even without any upgrade lately) which makes it expensive,
now offers no notebook for me.
So, i'll just keep my Late 2008 15" model running till the moment comes a 14/15 inch model is affordable ($1500 or so).
And yes, I use a 13" too every day, but connected to a big 27" screen on the job.
Conclusion:
* Create a Macbook Retina (non-pro) 14", i5, 8GB, 256GB SSD but do have the ability to connect to 4K screen (core usage: play video, do internet!), price it $1500, and Apple opens up a whole new market they never had.