Regarding ggplot2 and D3, it's already possible to draw ggplot graphics in the browser, consider looking at the following two repositories:
You'd probably want to speak to Hadley for more information on his goals, regarding ggplot2 & D3. I'd certainly like to try out any combination of these tools.
In my line of work, clients are more concerned about "out-vizzing" the competition by creating mind-blowing "Wow!" vizes. Doesn't this rule ggplot2 out for the most part?
While d3 is a great tool for analysis as well, it's more for presentation than exploration, I think.
R and ggplot2 are for exploration & analysis, with the added benefit that ggplot2 makes wonderful plots fit for publication. They're quite beautiful, and well done, but not creating interactive, shiny visualizations.
They all have their place in the ecosystem.