I see something different. There are more and more "console like" gaming PC. Steam introduce big picture mode (TV mode). Large TV is getting cheaper and cheaper.
There is a trend that to use TV for PC gaming. You may call it "non serious gaming". However, it's not about serious or not, but what people may do in the future (like the VR).
I am those kind of people will get whatever I want regardless the cost (as long as I can afford it), but the majority of gamer do really care about the cost. That's why 1080p still the majority at this moment (relatively low system requirement, and good cost to performance ratio).
If we consider these factors as well. I can't see how the ultra wide monitor can be the winner. It's relatively expensive because of that "unusual ratio", quite a lot of gamers will just get an extra 1080p monitor ISO "upgrade" to the ultra wide. I hate any gap between monitor, I will never do that (That's why I get a 84" 4K TV for gaming), but most of the gamer will just accept it because they want to lower the cost and get more pixel at the same time.
The input lag on the TV is huge if compare to a gaming monitor. However, again, it's not about how serious in gaming, but the cost to performance ratio. Most of the TV now offer TV mode or PC mode, this mode has much lower input lag (still not as good as the monitor, but already good enough for gaming). Including myself, quite a few of my friends already use TV for gaming. Just few hundred bucks can get a 42" 1080P TV, which is good enough for 1080 60FPS, then why spend the same amount but get a much smaller monitor? And now, the 4K TV has HDMI 2.0, so 4K 60PFS gaming is possible. And once again, 4K TV usually much cheaper than 4K monitor (for the same size). For gamer, this is a good news. As long as they have HDMI 2.0 output, and don't care about that little extra input lag. 4K TV is good for all 1080P, 1440P and 4K gaming. Even the PC can only output 1080 60FPS, the upscale / AA function in the 4K TV may make the picture looks better than normal 1080P picture, this is the extra bonus, and something that the monitor cannot offer. A little bit extra input lag but better picture, sounds like a good trade off for some non serious gamer like me.
In the Nvidia website, there is a page to help the gamer to choose the right GPU. Only 1080P, 1440P, and 4K avail on that page. For me, that means even Nvidia assume these 3 resolutions are the most common current and future resolution, but not ultra wide.
The ultra wide monitor may be the future for the serious gamers, but I don't think it will be the next most popular resolution for gaming, because TV may become more and more important on PC gaming, but only very very few TV offer ultra wide resolution.