3 ?
6 is dead 7&8 are still around and 9 is pretty decent. That leaves two more to go.
I wonder if ten years from now IE 9 will take the place of IE 6 takes today...
The best hope to get rid of IE 8 is the same thing that killed IE 6 for good: popularity for the recent version of Windows. If Vista didn't falter the way it did, we would have had less time on IE 6, due to adoption of Vista's preinstalled IE 7.
Perhaps the solution is to develop a flash replacement for the HTML5 elements that we can then force feed IE and all you have to do is include that script on a page to give your users a modern expericence, even if they have to be dragged into it.