There is no typical lag. Also, OpenACS is going to very clearly expand into its own product. With version 4.0, modules will be either ACS, OpenACS, or both. OpenACS 4.0 core will support the same API as ACS core 4.0.
So the real response to your question is: we are not porting 3.3 or 3.4. We are going to start soon on 4.0, and the goal I'd like to see us hit is a stable November 1 release. After that, things will be much more distributed in the porting/development of new modules. This will be independent from work on OpenACS core.
