Immersive 3D Web? What? You mean virtual worlds, right?
Repeated visitors to my blog will see this graphic again.
Almost all virtual worlds are "closed gardens". This is where the host company wants you to sign up for only their platform and keep you and your assets locked into that world. This is not the way the web works, but it is currently the way that the virtual worlds industry works. Sorry correction, I should say "is not working". Virtual world residents are demanding interoperability among worlds, transferring of virtual assets/avatars, and a host of other problems. So now different companies and institutions are all working on developing "open-standards" for virtual worlds.
Here is the funny thing. All 3D virtual worlds are an application of 3D on the web or web3D. Hooray! There already is an open standard for web3D, called X3D developed by the Web3D Consortium. But the virtual worlds industry doesn't want to use any part of it, or build off of it. They want to re-invent the whole thing (1 example).
Now I will spare you the details of the politics of past and present bad blood between certain people and companies that would make this collaboration difficult. Mention the web3D open standard in the virtual world crowd and you will hear, "you mean VRML?" from people who should know better, get an ear full from those VRML burned in the 90s on how "it didn't work then and won't work now" with the fire of a jilted lover, or be told how the standards body is "full of legacy pieces that move too slow".