I was in the market for a mba before I setteled for a rmbp 2013. settled on the rmbp because it was the best value and most future proof of the two models.
what I'd like to see in the next mba is a retina screen while maintaining the same battery life. this seems like a definite.
i'd also like to see edge to edge glass for the display. that razed gray bezel isn't very elegant and not apple like.
a deeper sd card slot. when using the sd slot a good portion of the card sticks out. all my other windows laptops have nice deep, spring-loaded slots that have the cards sitting flush with the side of the laptop.
i'd like to see touch id make it onto the laptops allowing for quick keyless login and quicker, more secure online shopping.
lastly with cellular data getting cheaper and faster, I'd like to see built in cellular chip for direct access to internet without having to go through a hotspot or trusting free wifi. basically have a sim tray on the side, so you can pop in a sim and whenever you're on the road, have internet as soon as you open your laptop.