According to this article over at The Inq, the new Palm OS 6 will be released to licensees before the end of October. The new version will focus on wireless technology standards, security and multimedia.
The same site has posted a Palm roadmap here with information on new Zire and Tungsten models to be released by the end of the year.

As a Palm owner myself and editor of TS, I'm afraid to say that the PDA market has been somewhat overrated or at least for the time being, PDAs would only seem to cater a very small niche. We have reported on bad sales figures of the devices before, in general I would say, until optimum integration with cell phones and a true convergence with PCs becomes a reality, the situation won't change a bit.