Samba Team member Andrew Bartlett has written a paper on Samba 3.0 / Samba4 integration. The paper explores past attempts at merges between the current production Samba 3.0 release and the Samba4 development branch. The paper moves through an overview of existing interfaces in Samba 3.0 and Samba4 and examines the possibilities for future integration between the two code bases and their vastly different interface designs.

This paper is targeted primarily at groups implementing Samba, and offers Andrew's perspective on questions that might arise from those currently running Samba 3.0 as a Samba4 release grows more imminent. It's a nicely written piece, certainly worth the time to read. So check out Possibilities for Samba 3.0 / Samba4 Integration.