When considering the future of marketing, with an eye to the year 2020, I think you are close to the right idea. Marketing as a business initiative will most likely cease to exist, and product placement and promotion will happen seamlessly in an immersive, highly personalized experience that bridges the real and the digital.

As a serial techie, a massive sci-fi geek and entrepreneur, I can see clearly that the future of any initiative to drive awareness - be it marketing, promotion, direct sales or driving brand recognition - Will be entirely driven by 3 factors:

1) Mass-market adoption of the technology required to access the new experiences - e.g. the internet in the "old days" and mobile in recent years

2) The social acceptance of that technology. Mobiles are ok, but currently Google Glass (potentially more immersive) is not socially accepted

3) The ease at which people can create and publish content within the new medium - If creating immersive 3D experiences requires expensive equipment or skills, it will always struggle to get mass adoption and social acceptance.

Well done on being so much of a forward-thinker - I'd love to offer my opinion in more detail via a call, but it is very much a speculative topic at this stage.

I think speech systems are the future of the web. I'd look at Andrew Ng's keynote here, full video is 1+ hour: http://www.lifehacker.com.au/2015/03/the-basic-recipe-for-machine-learning-explained-in-a-single-powerpoint-slide/

There have been several attempts in the past to build a 3D standard for web. Most, if not all, have failed. The main reason that they have failed is that they have required extensive 3D party plug-ins or additional software that bloats web browsers, opens additional security flaws, or is simply incompatible with a given platform.

There have been some advances made recently with the progression of WebGL, introducing a more accepted standard is widely used among all web browsers. Even with this technological improvement, there is still a lack of practical application for this standard to be widely used in everyday marketing. While I have seen some unique uses of 3D in product marketing (the Lacroix can designer comes to mind - http://mylacroix.com/), mainstream use of this type of marketing has still failed to gain widespread acceptance.

I feel that web based 3D will not really catch on until there is a significant number of connected AR/VR devices that can fully utilize the unique attributes of 3D. When there are users that can justify the cost from a marketing standpoint to fully integrate 3D design, then we will being to see a true evolution of 3D web-based technology.