Tim Bray has reported on a dynamic languages summit that was held at Sun recently. Aside from the timing (years too late), I think that this is a very positive development. There were key implementors of multiple languages (the notable exceptions being Lisp and Smalltalk folks), the list of stuff issues/features that was discussed seems to be the right list, and (most importantly) it looks like there is some acceptance of the fact that the JVM bytecode set could do more for dynamic languages.

My guess of a timeline looks something like this:
3-6 months to decide whether bytecode instructions are really necessary or not
Another year for a JSR to approve those instructions
Another year to do the work to the VM (including compatibility testing etc)
As much as 18 months (is the JDK on an 18month cycle now?) sync of with a JDK release, depending on the JDK schedule.

So, we're looking at 2 years (at least), or 2007, before anyone would be able to count on JDK support for their dynamic language implementation. Once that JDK ships, there's the typical adoption cycle, which means another few years before you'd be able to deploy a dynamic language solution on top of the JVM. That's a long time. Fortunately for Sun, there's not a lot of dynamic language support in CLR 2.0, and that doesn't even ship until 2006, or as late as 2007. So a MS designed and implemented dynamic language enhanced CLR could also be quite far off. 2010, maybe? It has a nice ring to it.

This means that anybody else has 2-5 years to get their act together and get going.