The rumored $1699 13" rMBP starting price doesn't really makes sense if it only comes with 128GB of storage.
That would be paying $400 more than for the equivalent 128GB/8GB RAM 13" MBA just to get a Retina display and a non-ULV processor that costs the same (both $225 OEM price).
The premium for a 13" rMBP over a 13" cMBP would also be higher ($500) than for a 15" rMBP over a 15" cMBP ($400) even though I'm pretty sure the Retina display in the 15" is more expensive/harder to make, plus it gets 256GB of storage which is considerably more expensive than 128GB.
I don't think Apple would have a significantly higher margin on the 13" rMBP than on the 15" rMBP. I have a hard time believing that. The specs may be wrong, the price might be wrong, or we may get a discrete GPU after all.