I'm going to offer up another possible scenario. Poke holes in it, discuss it further, do what you will.
One of the huge reasons that people in this thread are skeptical of Apple discontinuing the non-retina unibody MacBook Pro in favor of the new retina design, is that the price-points of the retina models are so high and that the resulting price gaps in Apple's notebook line would leave them without machines to sell at previously held price-points to people that would've previously bought machines of that calibur at those prices.
Another big concern is the sensitivity of the 13" MacBook Pro being Apple's best-selling Mac, according to Phil Schiller two months ago.
Given these, my possible scenario is this:
Say Apple, with the next refresh, discontinues the 15" non-retina MacBook Pro. While the higher-end non-retina 15" MacBook Pro held a spot shared with the retina 15" MacBook Pro at the $2199 price-point, there is now a vacancy in the $1799 spot previously held by the lower-end non-retina 15" model. This model, over the last three years (three revs) has had a weaker video option; whether it was 512MB of VRAM versus 1GB, or a 6490M versus a 6750M or a 6750M with 512MB of VRAM versus a 6770M with 1GB, there has always been a graphics disparity between the $1799 model and the $2199 model.
So, in the place of the $1799 15" non-retina model, Apple could put out a $1799 retina model that ONLY incorporates the Intel HD 4600 that is due to come out in Haswell. This IGP, while still not being as powerful as a discrete GPU, it still ought to close the gap that much more. This machine would be akin to the low-end model Mid 2009 2.53GHz 15" MacBook Pro model that only came with the NVIDIA GeForce 9400M IGP and without the 9600M GT that the higher-end models had.
The 13" Retina would likely drop in price by $100-300, making it $~1499 and $~1699. Apple, given the popularity of the non-retina 13" MacBook Pro, might elect to either issue it a silent Haswell update internally or to just keep the Ivy Bridge model around for another generation or to use the recently released lower-wattage models and keep it around for another year much in the same way that the iPad 2 has enjoyed a long stay of execution. Given the fact that the MacBook Air has more or less cannibalized the 13" non-retina Pro at the entry level, only the high-end 13" Pro might remain.
Given all of this, the MacBook line-up for 2013 could look like this:
11" MacBook Air - Low-end - $999
11" MacBook Air - High-end - $1099
13" MacBook Air - Low-end - $1199
13" MacBook Air - High-end - $1499
13" MacBook Pro (non-retina) - High-end - $1499
13" MacBook Pro (retina) - Low-end - $1499
13" MacBook Pro (retina) - High-end - $1699
15" MacBook Pro (retina; Intel integrated graphics only) - $1799
15" MacBook Pro (retina; Low-end with discrete graphics) - $2199
15" MacBook Pro (retina; High end) - $2799
(For those that fantasize about a 17" retina, insert those predictions at this end of the chart).
What say you all?
I'd rather see a 15" air in the spot where you put the 13" nonretina. That would actually be a good product at a reasonable price.