spigzone, your OP is a prediction that makes a series of assumptions. Namely that AMD will do no wrong and Nvidia will simply roll over. That key assumption is flawed by the state of each company's financials. AMD is making a move for market dominance, but they are doing so on the back of a series of layoffs, losses, and inferior product performance in the desktop GPU and CPU field.
Nvidia, on the other hand, has been quite content with its own hardware, which has at times outperformed faster AMD chips. The 700 series is better tuned than the 600 series, but uses the same silicon simply because Nvidia doesn't need to release anything better, at least not yet. I am sure that Nvidia engineers are hard at work on the next generation of Nvidia GPUs, and depending on where that generation is in development, it might be able to respond to the R9 290X and Mantle without losing much performance (if it isn't already accounting for it). And let's punctuate this by pointing out that Nvidia is in good financial state.
Those are the big ones but you do make other assumptions. Take, for instance, the role of consoles over the next 8 years or so. That assumes that these consoles will perform well, and that console gamers don't start jumping ship for alternatives, like Steam Machines. The price alone could be problematic if Valve can help bring down the cost of a living room PC, offering a more functional gateway to PC gaming. That is going to be a defining point of this console generation because both Sony and Microsoft have been and will continue to advance digital distribution, a field that is already dominated by Valve. If they can bring Steam to a console form, both companies will become very nervous.
That uncertainty casts doubt on the potential success of Mantle as well, and there's no guarantee that Mantle will catch on. And even if it does, that doesn't mean that AMD hardware will always perform better. As I already pointed out, Nvidia has been doing better with slower hardware, they've been posting profits, and they haven't had to release new GPUs or GPU architecture in some time because of their dominance. That gives them a lot of cushion to react to and potentially negate AMD's advantage.
It's fun to speculate occasionally, but understand that it is only speculation.
On second thought, let's not go to TechReport. Tis a silly place.