On the topic of the future of gaming laptops, as a representative and employee of a gaming laptop provider, I'm surprised to see the growth in mobile GPUs and their performance against desktop GPUs. Obviously, the desktop GPUs are still faster than their mobile counterparts, but the performance gap shrinks each year, which I find incredible.
MSI's GT series are powerhouses that run tremendously well against desktops with the added benefit of portability. I can see gaming laptops as the future of gaming and the growth is only going to continue. Take for instance MSI's GT80 with its mechanical keyboard (I've seen and tested this in person) and the machine is truly amazing. Who would've thought that a mechanical keyboard could fit into a laptop.
As companies continue to push the boundaries of technology, we can soon see laptops as a standard versus desktops. The world is becoming more portable and gaming will follow this trend, in my humble opinion.
On the topic of a dual GPU, I'd recommend against a dual GPU and maybe just opt for the single-GPU 980M. Dual GPUs have a huge problem with cooling and even with a cooling pad underneath, your laptop runs danger of overheating. There just isn't enough airflow in laptops to allow for a cool SLI experience. A 980M will last you for years and keep in mind, new GPUs are incremental performance increases from the old generation.