2019 minimum. 2017 would be a spit in the face to the supporters who bought the Xbox 1. It would be worse than Nintendo releasing the NX this year considering Nintendo are known for not supporting their consoles for long whilst the 360 had 7-8 years of support.

I doubt uncharted 4 has that much of an effect, but I see the reason behind it, I still think it's a bit too early to say the Xone is already doomed and a new Gears and QB can still do wonders for the Xone. Besides Sony surely will screw something up, but MS got to have a wonderful E3 to assure gamers the Xone is still a good console and worth owning for various reasons, bringing exclusives to PC just isn't, but if I look at Splatoon one might say everything is possible.

2017? Absolutely not. 2018? Possible, but highly unlikely.

I am banking on 2019, 2020 at the latest.

I won't be surprised if they dropped the console earlier. People are distracted by even bigger fails (PsVita and WiiU) but the XboxOne is doing badly.

Comparisons between X360 and Xbox One don't really make much sense.
The X360 (and Ps3) were pioneering consoles designed to introduce a new format (HD gaming /entertainment) and were meant to have a slow start but to run for years. In 2005, the vast majority of people didn't even had an HD TV to play with, while the most obvious benefit of X360 were HD graphics.

Ps4/XboxOne on the contrary are market-driven innovations, they've offered a graphical upgrade because the market was demanding it. Market-driven innovations are supposed to have a strong start, but to have a short run.

So, comparing X360 sales to Xbox One sales is like comparing the pace of a marathon runner with that of a 400m runner.

Can't imagine this to happen.
The most early release I would expect is holidays 2018, but something between 2019 and 2020 is more realistic imo. I would predict 2019.

It's hilarious that two of the few people that don't even see the possibility of a Wii U successor after 4 years are seeing 2017 for the XBO successor as one of the "most probable years" although the XBO is selling much better and has also much better acceptance/support by third party developers/publishers.

Sony, will never let Xbox, launch 1 year before Playstation,  if they release in 2017, is too soon, they would have 1 year less life-time than the Wii U.

If it releases in 2017 the thing will be barely more powerful than the PS4. Remember that these things need to be cheap. Microsofts only option are pretty much AMD APUs and currently there's nothing mind-boggling in sight in that regard. So unless Microsoft is looking for an expensive as fuck solution with discrete graphics chip (doubtful) or are currently engineering their very own Chip Design (VERY doubtful) we won't see a new Xbox before 2020. 2019 at the very least.

Whichever the year, I am sure it will be 1 year before the PS5. Because it has become evident that Xbox cannot compete head to head with PS. 360 having a year head start did wonders for the system, with an extra year of sales and most games coming out on PS3 1month-1 year later.
2019 is my guess, but if PS5 is planned for 2019 then they will launch in 2018.

2019.