People seam to forget 1 very important difference between consoles and PCs. While consoles will no doubt be out of date within a year or 2 in terms of hardware, but despite being aged the low powered consoles tend to be far far more efficient than your average PCs because:
1: Direct hardware access, no OS footprint, means much much better utilization of the hardware compared to PCs. That is, a low end console can match and surpass a highend PC for a good length of time. Just look at PS3 and 360, 7 year old hardware and still producing amazing visuals.
2: Hardware is fixed, not only it makes a developer better design games around it with better control on quality and less bugs, but games evolve technically for several years as developers get familiar with inner workings of the console. PC is more 'waste' as hardware upgrades so fast with thousands of different configurations, it is just simply not possible to produce the same level of quality over the game.
So yeah, basically PS4 and Next Xbox should be able to hold their own against the PCs just fine for several years. Now that the hardware is in line with PC architecture, it should be even better for types of systems.