Typically, consoles manufacturers have favoured higher performance memory rather than more memory ...
I don't think that a system could be affordable with 8GB of high performance memory (and certainly not with 32GB of high performance memory), and I'm not sure if developers could get the kind of real world performance out of lower performance memory.
Essentially, I suspect Microsoft and Sony could get 8GB of DDR3 2000 (PC3 16000) memory, but I doubt they could afford that much of DDR3 2800 (PC3 22400) or GDDR5 memory.