It's no surprise that apple had to discontinue the white macbook. i too loved it as an everyday use computer but the core 2 duos were phased out by the time sandy bridge came along, and sales were increasing on the macbook air and slowly decreasing the macbook, because of outdated technology. the macbook was once the computer of it's time because of it's price point for an apple mac and with some decent technology that made it usable compared to the macbook airs back in 2010.
Well, Apple probably made the white MacBook outdated on purpose. You should remember that the white MacBook was redesigned in late 2009, and it got a polycarbonate unibody, one year after the release of the aluminium unibody. A new design.
The last version of the white MacBook had a Core 2 Duo processor, which was already outdated at the time. But, at that time, the aluminium 13-inch Pros also had a Core 2 Duo processor. The reason behind it was that Apple wanted to (or had to, due to contractual obligations) use NVIDIA integrated graphics solutions (the 9400M and the 320M), which were far more powerful than Intel's integrated graphics cards. However, Intel sued NVIDIA to prevent it from developing those integrated cards for the Nehalem processors. Therefore, to continue using NVIDIA solutions, Apple had to stuck with Core 2 Duo processors in all the laptops that used integrated graphics cards. This is why the Core 2 Duo processors were used in both 13-inch MacBooks and MacBook Pros until 2010.
Apple updated the MacBook Pro line to get Nehalem in early 2011 (dropping the NVIDIA integrated card), and it could have updated the white MacBook too. Instead, it chose to discontinue the MacBook line in favor of the MacBook Air. It was not due to technical restrictions. It was a business decision.
maybe the same thing will happen with macbook pros in the shift to retina? more sales on that over the classic MBP will move apple forward to include as standard in two years?
I don't think Apple will keep three lines of 13-inch laptops (the 13-inch MacBook Air, the 13-inch MacBook Pro and the 13-inch MacBook Pro with retina display).
In the next refresh, it may (i) merge the 13-inch MacBook Pro and the 13-inch MacBook Air, keeping just one 13-inch laptop; or (ii) keep the current 13-inch MacBook Air and releasing a redesigned 13-inch Macbook Pro with retina display. In any case, IMHO, the current 13-inch MacBook Pro will be gone. There is no sense in keeping it.
Apple are doing this right now. why do you think that apple named one macbook the 'pro' and one the 'air'? i agree with you that both should have different price points because of the differenciality between them, with the macbook airs being reduced a bit more in price in the near future.
I agree with you that Apple diferentiates the products at some point. The MacBook Air is marketed towards consumers, and the Pros towards professionals, prosumers or whatever.
I also agree with you that the price point should be different.
I wish that Apple would reduce the price of the MacBook Air. But, you know, that's Apple. Apple may well choose to raise the price of the MacBook Pro instead.
I agree with you in a sense that this has already happened before, with the macbook airs soon replacing the old poly macbook. but it not being an experiment? I don't think so IMHO. the macbook air, when it was released back in 2008, would have been an experiment to see the markets movement on computers, and look what a success it turned out to be. And I generally think the same with the retina macbook pro because it is a first in apple's mac line, in which i see the design of it becoming standard across all macbook pros in a couple of years time. sorry to keep banging on about the future of the retina macbook pros here, saying that retina will be standard in a couple of years and all that, but that is the way i see apple are headed for in the future, as competition rises for displays and prices for quality.
I see the new design becoming stardard very soon. Next year probably. Retina displays should be cheap enough to put in all Apple laptops. A 1280x800 display costs almost nothing these days, and the retina displays, although much more expensive, are not prohibitive. SSDs, however, are still very expensive.
Note that Apple has products for all price points, and usually it has only one product of a given segment for that price point. The exception here are 13-inch Pros and Airs, which occupy the same price point. There may be (and there is, for sure) some degree of cannibalization between them. Please see if these price points make sense for you in the next generation of laptops:
MacBook Air 11" low end: US$ 999
MacBook Air 11" high end: US$ 1,099
MacBook Air 13" low end: US$ 1,199
MacBook Air 13" high end: US$ 1,399
MacBook Pro 13" (retina) low end: US$ 1,499
MacBook Pro 13" (retina) high end: US$ 1,799
MacBook Pro 15" (retina) low end: US$ 2,199
MacBook Pro 15" (retina) high end: US$ 2,699
apple may want to take advantage of Intel's lowest-end in their macbook airs, but i don't see it happening in their macbook pros. yes, we might see a voltage reduction in the MBPs, but not one with a voltage as low as that of the ones speculated for macbook airs.
The low-voltage processors are not necessarily low-end. They are just low-voltage, but they may be high-end. In general, these processors may be slower than standard-voltage processors, but there are always trade-offs: they have a better battery life. Apple may choose to continue using low-voltage processors in the Airs to make them even thinner and lighter.
I seriously doubt there is a voltage reduction in the Pros. Intel has not made any custom chips for Apple for a while. Haswell low-voltage processors will have a TDP of 10W. Standard-voltage laptop processors will have 37W. No in-between announced so far.
how would it put it in different segments?
Price. Apple once had 12" iBooks and 12" PowerBooks. iBooks were much cheaper than PowerBooks. Simple as that.
i see where you are coming from, but looking at apples iPerspective

D), would they want their machines being a different design to other apple macs? do they really want to sacrifice their perfect recipe of formal and great to use in their already existing products for the sake of lightness? i honestly think right now that the macbook airs are light enough as it is, and the same with the macbook pro.
I agree with you. But Sony and other companies are already making carbon fiber laptops. Apple once had the thinnest and lightest laptop in the world. Now it doesn't. And what if everybody else turns to carbon fiber? I don't know if Apple will adopt carbon fiber in the future, but it has to investigate this possibility. Apple wants the lightest products in the world - the iPhone 5 is announced as the lightest and thinnest iPhone ever. Look at this:
https://www.macrumors.com/2012/09/26/apple-sourcing-carbon-fiber-components-for-upcoming-product/