Completely disagree. A single 1080TI will finally be "good enough" for a lot of high resolution / high frequency use cases where you had to go SLI before.

I find it useful to multiply resolution with refresh rate to arrive at a number that indicates the number of pixels being pushed per second:

  1920x1080 x60  =   124,416,000
  2560x1440 x60  =   221,184,000
  3440x1440 x60  =   297,216,000
  3440x1440 x100 =   495,360,000 
  3840x2160 x60  =   497,664,000
  2560x1440 x144 =   530,841,600
  3840x2160 x144 = 1,194,393,600

So there you go - a maxed out 34" ultrawide has just about the same requirements as a 60hz 4k monitor. Yet a normal 27" 144hz will out-require both of them ... and they come in even faster variants yet!

Edit: And then you start seeing 144hz 4k screens; you will still find yourself wanting with a single 1080TI.