From what we can hear/read already (results, interviews, linkedin, etc), the "official" next cycle will begin in 2017 if you count Nintendo (or even a bit earlier) and not counting handhelds, Fall 2018 for the others (with obviously a window where they could wait a year depending on strategies and manufacturing/design problems).
I think that in terms of games, crossgen will end around 2020 (a bit like we're finally starting to not have crossgen titles anymore this year).
For the "wow" factor, it's a bit more complicated.
I doubt Nintendo will release a really powerful console, but still noticeably more powerful than the PS4/X1 (but sadly having a different architecture once again, damaging the final port quality), and Iwata already confirmed some sort of "gimmick" (not a fan of the term, but to understand better) to go with it.
For the PS5/Xsomething, I think it will mainly be perfecting what they tried to do this gen (focus on online, sharing with others, "all in one entertainment system", bigger space drive for more digital games from start, 1080p, etc), while allowing more options for the consumer. Basically streamlining PCs. More control options (KB+M), even easier for devs (indie or not), VR at good quality, things like that.
Not a Wow factor, but perfecting it. Didn't see a wow factor for this gen either tbh, apart from a good sharing UX.
Last gen was an anomaly and lasted way too long for good reasons (expensive architectures, start of HD development, industry behaving differently than before, studios disappearing, digital games, indies, etc), this gen is there to get back money, and the architecture is simple enough to get great results from start.