I can see them slimming the 13" model down as they did with 15".
I mean their roadmap seems pretty clear to me:
- Macbook Airs will be what Macbooks/iBooks were: Apple's consumer laptops with low pricetags
- Macbook Pro's w/ Retina display will probably drop the "Retina" part and will be Macbook Pro's in 13" and 15" variants aimed at power users
So yeah, I don't see MB Airs getting Retina displays, at least not for few years, the reasons behind this are: price, battery, market.
I think 13" MBPr will be underpowered as classic 13" MBPro - it is sort of "Pro" laptop (you can edit HD videos on it, do Photoshop work) but there is always one thing missing - beefier CPU or dedicated GPU (depends on person).
My prediction: dual-core CPU, integrated GPU, 4GB RAM
BUT I can see them cramming at least SSD in there since the new redesign doesn't count on moving platters.
The price will come down, just like it did with Airs but now, it'll probably be more expensive that classic 13" MBPro.
Classic unibody Macbook Pro's will stick around for a year or so, then they might get rid of them (or move 13" model to educational store) and drop the price to match it.
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So why call it the MacBook pro, after all of the work that they've done to distinguish the new retinas as "professional" machines?
Pro's on budget. College kids studying digital arts who work with AV applications.
The 13" has proved to be very succesful because it's cheap and you can do a lot of stuff on it (albeit with some limitations). 13" MBP was my first Apple computer and I loved it (until my needs were bigger).
The great thing about unibody MBPs is/was their expandability, you can easily cram SSD and 16 gigs of RAM in there for low price now. With new models, they'll probably lose this advantage.
Let's just hope they will at least offer more RAM as BTO like they do with Airs, but for 16 gigs.