I guess you might be stating my opinion; but my thought is why? What is the 3d web going to give me that 2d doesn't?
It might be helpful to consider an analogy: "What is the 3d desktop going to give me that 2d doesn't?".
The first stab at '3d web', the ghastly VRML horror, is very similar in spirit to the various abortive attempts at creating '3d desktop' graphical shells. As it turns out, this is an area where you are lucky to break even with what you are trying to replace, and epic failure is the rule. Such attempts have largely died, and deserved it.
'WebGL'(as its name suggests) is much more closely aligned to '3d desktop' in the sense of 'people writing programs for this platform can expect OpenGL and/or Direct3d to be available to their programs if they want it'. This has proven to be enormously useful: lots of applications are simply impossible in anything approaching real time on affordable hardware with a pure-software render path, and the bad old days of having one variant for 3dfx/Glide, one for software, one for openGL, and possibly one or two others for oddball losers like 'S3 METAL'.