A "Lab Preview" of the next version of Personas is being demoed in several sessions at Sapphire this week. This version is HTML-based (no Silverlight required) but with broadly the same functionality as the current Silverlight version. Of course, no promises are yet being made about the availability of this version, but "before the end of this year" was mentioned as an aspiration.
There will be an automated migration process for converting flavours in the current version to flavours in the new one. Whether that is a complete conversion or will require manual work also is yet to be seen. It may vary depending on the flavour.
So, starting to work now in Personas v1 will not result in lots of wasted work, and while the technical details of how you build flavours will change in future, the higher level principles of a Personas project will not. Anything you learn about where/when to use Personas v1 will apply equally to v3. If you think Personas might be of use to you, I would certainly start looking at it now and not wait until the new version is released. You just might want to hold off on building anything very complex.
Oh, and by the way, make sure you read this news - SAP Screen Personas now included with underlying SAP licenses
Steve.