I remember a while ago someone photoshopped a white macbook air it was like an ultrabook.
If they released an "ultrabook" white plastic macbook with a 1280x800 display, maybe just 1 thunderbolt, and 2 USB ports, no SD slot, and just thick enough to still use a conventional HDD, and no optical drive. Even with an i3 and i5 options, no i7, I'd get one, and I'm sure many others would. It could be a little bit like retina form factor with less functionality.
The problem is that the pricing it would either be just like the Air or the 13in Pro. Apple would be eating into the profits from another one of their models.
I would get an 11in Air with i7 and 8GB today, but I just want higher resolution than the 11in. and when i look at the 13in I hate that for a similar price the 13in Pro has better CPU and upgradeability but not the resolution.
I would love if the name MacBook came back, but it would have to in some w ay be a compromise between Pro and Air and there is just not a good place between them. Unless you take the Retina form factor, put in slower SSD, remove the SD card slot, 4GB of RAM and the 1280x800 resolution. As I said before though then why not just get an Air?
I think I just talked myself in circles.