Jeff Rizzo created the NetBSD 4 branch yesterday. It will result in the NetBSD 4.0 release in a few month from now. I’m personally not convinced that NetBSD-current was ready for this. There are e.g. compatibility problems between GCC 4.1.2 and GDB 5.3: you have to compile binaries with -gstabs or GDB won’t be able to load a core dump written by a program.
I however see Core’s point that branching now will probably help to stabilize things after a few weeks. But it will probably require a lot of pullup requests and therefore a lot of work by release engineering to get there. 🙁
But maybe there is no better way to deal with such things in large Open Source projects.