Simply put, there aren't any major changes for Nouveau right now as it concerns power/fan management. There is some out-of-tree Nouveau fan management code, but it hasn't been merged yet since it's potentially dangerous if something goes wrong and your graphics card ends up overheating.
From last month is my 14-Way Comparison Of NVIDIA vs. Nouveau Drivers for those interested, which includes not only the OpenGL performance numbers between the NVIDIA Linux drivers but also power consumption levels. Nothing in mainline has really changed to affect these numbers in the past month.
What is new to say though is that Red Hat's Ben Skeggs is working on the power management support for Fermi, the GeForce 400/500 series. The Nouveau Wiki has been updated this week to reflect the Fermi PM as now being a work-in-progress for NVC0-Fermi. It would be lovely if some parts of Fermi power management (especially re-clocking support) were ready for the Linux 3.3 kernel, but I haven't seen any patches yet nor heard any positive information.
As for the official word, power management for all generations of NVIDIA GPUs from the NV10 (GeForce 256) through Fermi are marked as being "WIP" on the aforementioned Wiki page.