I never suggested that we would see 32GB MBPs this year. (For the record, I think it's implausible given that we can't yet get 13" rMBPs with 16GB.) I did suggest that we might see 16GB 13" rMBPs introduced this year (possibly as a BTO option). The memory cost would be approximately the same for the 13" as for the 15" models and the space constraints could be overcome as described previously.
BTW, I believe the cost difference would be trivial between two 4Gbit dies each one on its own chip versus those same two 4Gbit dies combined onto one chip. Would you agree?
I didn't mean to imply anyone was suggesting anything specific. I just want to clear up comparing the MBA LPDDR3 memory to the rMBP DDR3L memory.
I only think the 13" rMBP would support 16GB if the number of DDR3L parts are increased to 32 from 16 and I'm not sure there is room for that on the board to do that or not.
The overall cost of two single die 4GB parts would be less that the cost of one dual die 8GB parts assembled onto a board from everything I have seen for overall product costs.