Classical raytracing by itself is highly unrealistic unless you also implement an add-on physical-based rendering-equation-solver such as Path Tracing or Photon Mapping. The first one beginning highly noisy and "converging" to photo-realistic over a looong time -- the second being only as realistic as the number of photons your hardware can manage.
Now without such a physical-based rendering-equation-solver, realtime raytracing of "simple scenes" (couple of spheres and boxes) is doable today. The more complex your scenes get (even with acceleration structures), the more you need to lower your viewport resolution. Your high-end desktop GPU can then handle raytracing for a low-end "mobile" resolution such as 320x240 or whatever. But your low-end mobile GPU probably can't. Also for fully accurate antialiasing you'd need to render at 2x your resolution and downscale.
tl;dr: realtime raytracing of simple scenes is feasible, realtime photorealistic full-screen antialiased raytracing of complex scenes isn't and if current tech development trends continue, won't be for another decade perhaps.
I don't see "we're really close to pulling it off" because as GPU flops and caps happily increase, so do unfortunately screen resolutions. In realtime raytracing, we're always lagging behind and always have to compromise: (1) high resolution, (2) antialiasing, (3) complex scenes, (4) photo-realism -- for real-time speeds, pick any two.
I didn't read the grandparent as saying we are really close to real-time path tracing; I read it more as real-time rasterization is getting rapidly closer to looking like path tracing both in the quality of the scenes and the types of scenes it can represent.
Also FLOPS has been increasing much faster than resolutions. 1920x1200 is about 3x the pixels of 1024x768. Graphics FLOPS has increased way more than 3x since 1024x768 was considered a high-resolution screen.
Now without such a physical-based rendering-equation-solver, realtime raytracing of "simple scenes" (couple of spheres and boxes) is doable today. The more complex your scenes get (even with acceleration structures), the more you need to lower your viewport resolution. Your high-end desktop GPU can then handle raytracing for a low-end "mobile" resolution such as 320x240 or whatever. But your low-end mobile GPU probably can't. Also for fully accurate antialiasing you'd need to render at 2x your resolution and downscale.
tl;dr: realtime raytracing of simple scenes is feasible, realtime photorealistic full-screen antialiased raytracing of complex scenes isn't and if current tech development trends continue, won't be for another decade perhaps.
I don't see "we're really close to pulling it off" because as GPU flops and caps happily increase, so do unfortunately screen resolutions. In realtime raytracing, we're always lagging behind and always have to compromise: (1) high resolution, (2) antialiasing, (3) complex scenes, (4) photo-realism -- for real-time speeds, pick any two.