As has already been said if the MBA gets a retina screen then there will be pretty much no point in buying a 13" rMBP. Again if Apple doesn't give the MBA a retina screen people will go elsewhere to buy an Ultrabook. I'm wondering whether Apple may ramp up the 13" rMBP model with possibly a quad core or a dedicated GPU. Thus producing a gap between the MBA and the 13" rMBP.
In my opinion a quad core is quite doable in a 13" laptop and although Haswell is bringing in better graphical capabilities a pretty low down 700 series from Nvidia could probably pull ahead.
In my opinion a quad core is quite doable in a 13" laptop and although Haswell is bringing in better graphical capabilities a pretty low down 700 series from Nvidia could probably pull ahead.