rMBPs may get classic MBA shape in due course!
I loved, loved, LOVED my 11" MBA for its portability, yet expandability (at home I would hook it to an HDMI display, do video and photo-editing and even the cheeky Minecraft session here and there).
The New Macbook could never replace this machine for me (also what on Earth is up with this gaudy gold colour recently?) - but I don't think it has to. It is a completely different machine, not meant for me and my usage. Instead, I think that the rMBP-line will take over the aspects of the MBA line, which I grew to love so much, and combine this with the rMBP's processing power.
The rMBPs will get thinner and thinner and perhaps the same wedge shape as the MBA. They will keep a substantial amount of ports (perhaps drop the Thunderbolt if Apple really doesn't see a future for this technology). With the rMBPs undoubtedly getting thinner and more battery-efficient, Apple had to come up with something initially extreme looking for the ultra-portable line, otherwise the classic MBAs would have soon been indistinguishable from the ever-thinning rMBP line and Apple would have cannibalized sales left and right.
So, that's - in my opinion - the strategy behind this weird new Macbook. It's not meant to replace the MBA line, because in very due course the rMBPs will merge with the classic MBA line combining the MBA's thinness with the rMBP's productivity. So if anything, the future rMBPs will "replace" the classic MBAs plus adding power.
If anything is being dropped, it is the notion that laptops for productivity must automatically be in a heavier, fatter category. The future rMBPs will be thin like classic MBAs and the ultraportable line is hence becoming thinner and thinner (some users may argue unnecessarily so) to retain a distinction between the two product lines.
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PS: Speaking of "dropping". I could imagine a large reason for the lack of the MagSafe is that the new Macbook is too light for it to work. I knocked my 11" MBA a couple times off the table when I fell over the cable, because it was so light, the MagSafe wouldn't go off in most cases. With the new Macbook being even lighter, I can see the MagSafe becoming even trickier to engineer...