It's not, though. Retina displays still use the same subpixel rendering and type AA as non-retina displays.
Yes, of course. That's still pixels, they are only smaller. It's still possible to render anything on a screen with AA, and at a sub-pixel level if wanted. And it can only get better with, in general.
It's the case on the retina MBPs if I'm not wrong, at a sub-pixel level. But to my knowledge there is only AA on iOS devices (retina or not), but no sub-pixel rendering.
And I don't know of any other devices/OS using the same approach as Apple, with constrained environment at fixed resolutions, and 'simple' pixel-doubling (... well, not on rMBPs. But as said before, sub-pixel rendering is here to help on OS X. Our discussion is more about iOS I think). Any other platform on 'retina' screens (people using the term only because of high enough pixel densities) do non-integer scaling (I might be wrong with Win 8, though, I think it's supposed to do 2x too). And doesn't it add problem of non-alignement with the pixel grid, making even more critical the need of sub-pixel rendering? I'm not sure what you suppose when you say 'retina'.
Doubling of pixels isn't enough to make up for the difference. 5-6 times the number of pixels and you're getting somewhere.
Hehe yes of course. Well, I'm a patient guy, the 'retina' screens we now have are quite already very nice. That was a big step to reach, with the hardware able to drive them, and with size and battery constraints handeld devices have. It can only get better.
Without antialiasing and subpixel rendering, that extra pixel doesn't really achieve very much at all. It's still limited to 45-degree angles by stepping.
As long as screens use pixels, and working or not at a sub-pixel level (offering more flexibility), that will always be true. The smaller the pixels goes relatively to the use distance, the less it is important.