WebGL can no longer use cross-domain textures in Firefox 5
developer.mozilla.org
developer.mozilla.org
A large part of people is using the web for (casual MMO) gaming. 3D gaming is very popular and attracts users. Currently this involves hacks using clunky applets (such as java3d). With WebGL, this will be a thing of the past.
3D in the browser has been tried before with VRML, which failed. One of the reasons for failing was that is was too high-level. Most game devs want to use low-level APIs such as OpenGL. Hence I think WebGL will be huge success.
A single uncompressed 1024x1024 RGBA texture is 4MB, for example.
(I say all this not to be negative, but rather in hopes that the correct developers will hear the plea from the indie game industry: enhance Local Storage. We want to build games on your WebGL platform, but we can't until you do.)
There are probably some other practical issues left to be resolved as well before the browser is a mature cross-platform 3D gaming platform. But I can certainly see things going that way.
Also, OpenGL isn't that low-level anymore. It is the API that the GPU speaks, and with recent developments the client can be much less 'chatty'. Do as much as possible from shaders and on the GPU itself. We've gone far beyond "do a call per vertex".
As for hope, yes I have more "faith" in Google/Mozilla to improve cross-platform javascript performance and memory issues than I have in Oracle or Adobe to improve theirs.
It has a very good chance of replacing casual Flash games, however.
I think it's important that WebGL gets pushed to the browser. Getting a stable 3D environment is super important for application development and obviously games.