Your not going to see a "proper" next gen if your expecting a PS2 to PS3 level "leap" in performance. Its simply not going to happen again like that unless some incredible breakthrough happens, and you'll know about the breakthrough because you'll see it on PC first.
The PS5, (Xbox X2 or whatever its called) will likely be backward compatible with this generation simply because the machines will once again be mid grade gaming PCs. It simply costs far far too much money to R&D your own custom GPU/CPUs like they did in previous generations and so if they want to use the fastest GPUs and CPUs on the market they are going to be choosing from the same pool of parts PC gamers choose from.
The difference in fidelity between a game at 1080p on a 1050ti and the same game at 1080p on a 1080ti is slim. It gets wider at 4k simply due to framerates but visually its still not earth shattering. The only areas consoles really lag behind right now are CPU capacity (which is an issue on games with lots of physics or interactive environments or BR style games) and in framerates.
I suspect the next big push from a PS5/new xbox will be higher framerates at both 1080 and 4k, hopefully a minimum of 60fps. Hopefully a push for freesync and HDMI based variable-sync, and a continued push for VR and AR capabilities.
