I'm wondering what type of process, if any, will be available to upgrade ISPCONFIG v2 to v3 when the final version is available?
There will be no direct upgrading option available. The reason for this is that ispconfig 3 has totally different system requirements so that a system that has run ispconfog 2 before is not able to run ispconfig 3 without a complete reconfiguration or better a reinstallation.
I hope that we will be able to implement some kind of migration tool thats is able to import the website and user details from a ispconfig 2 system to a ispconfig 3 system but there was no time yet to write such a tool and my priority is to get the final of ISPConfig 3 out at the moment. We will not stop the support and updates for ISPConfig 2 so there is no need for fast a upgrade to ispconfig 3 from a technical standpoint.