Few things:
1) GT3e will consume more power, and put out more heat, so you either have a quad-core chip with GT3e, or a quad-core chip without GT3e but with dedicated graphics. Not both.
2) Radeon HD 8870M is way beyond the thermal design target of the current rMBP, and the current rMBP is already showing signs of throttling depending on conditions. If Apple is using something with similar thermal target from AMD side, then it absolutely has to be something along the line of HD 7790M or 7850M. And also along that line, you can forget about 2GB GDDR5.
3) There is no 32GB modules available, so it makes no sense for 16GB to become standard, as then there would be no point in offering any "upgrade" other than processor and storage space. That said, 8GB is likely to remain as standard for a while yet.
4) Unless Apple uses a new screen technology, it's doubtful that the current screen can get any brighter without sucking battery life like crazy. So another no there.
5) I think Apple may decide to keep an older generation rMBP around at the $1999 price point rather than offering a new rMBP at $1999. Either that or the $1999 rMBP won't have discrete graphics.
Seriously, it's a $200 price drop. Something significant will have to give.
So I think you are off by a pretty huge margin.
I agree with you.