There is no info about this kind of Notebook. ASUS mainly relies on single GPU configurations and I do not think that they will want to invest time and money into a "more than desktop replacement" gaming laptop. Even with their cooling solutions, the current cases won't accept a SLI configuration so they will have to pay another team of engineers in order to come up with a new case, along with a design team for the case and blah, blah... It is an entire process that in the end won't get them any more money than they get from the single GPU models. A SLI model would definitely be much more costly, and it will be more than a desktop replacement laptop in terms of weight and size.
I do appreciate ASUS here for their consistency because in the past 2 years they managed to offer one of the most inexpensive gaming notebooks just by keeping it simple (without too many additional, unnecessary features that add to the final price of the product).