Nintendo could plan to counteract the arrival of the PS4K and XB1.5 by offering an initial console that is around the current level (PS4) and then add the SCD as a much cheaper way to stay within touching distance of the PS4K at a far cheaper price, considering that all they would need in it are updated GPU/CPU and RAM and they can save on other components like controllers, disk drives, etc...
Might be an attractive and cost effective way to have a powerful console for consumers, especially if the PS4K is $400-500 and meant to be used with the PSVR (another $400).
My concern with this is that what you'll have is this situation:
The leader of the generation by a LONG shot making a much more powerful machine
The loser of the generation that almost NOONE gives a shit about any more, finally catching up.
The former will likely have backwards compatibility
The latter may or may not but who cares for the 6 good games
Who do you think people will go for? Basically for Nintendo to get the enthusiast gamer back they would need a machine of such great power and features that the PS4 looks like a calculator. There is no way Nintendo will do that. Nintendo know their place in the market - Japanese handheld gamers and Nintendo fans.
I PS4.5 wasn't coming I would have thought Nintendo might be able to sit another 4-5 years out with a comparable machine until the PS5 comes and then refresh and keep in lockstep tech-wise. Now I'm not so sure they can do it.