NVIDIA has previously said that their 306 Windows graphics driver will remove support for the GeForce 6 and GeForce 7 series graphics processors. With the largely shared code-base between Windows and Linux/Solaris/BSD, it could be presumed that they would be removing the support for all platforms. NVIDIA's Hardy Doelfel confirmed to me today that it's indeed the case.
The NVIDIA Linux (and Solaris and BSD) 304.xx series is the last that will support the GeForce 6 and GeForce 7 series. Following the end of the 304 series, NVIDIA will maintain that as a new legacy driver branch. If it's maintained like previous NVIDIA legacy branches, they will provide new Linux kernel and X.Org Server compatibility for this hardware along with important bug-fixes, but not any new driver features and capabilities. The NVIDIA 304.43 Linux driver was released earlier today as the latest version in this current series.
NVIDIA's Hardy Doelfel wrote, "Michael, you are correct. I will be posting an official announcement the next few days that 304 is the last release branch for some cards, including GeForce 6/7, making 304 the next legacy branch for these GPUs."
NVIDIA's current legacy driver branches include the 71.86.xx, 96.43.xx, and 173.14.xx series, soon to be joined by the 302.xx series when dropping the GeForce 6/7 series support. The GeForce 6 "NV40" series was introduced in 2004 while the GeForce 7 "NV50" / "G70" series launched shortly afterwards.
NVIDIA dropping the GeForce 6/7 series support from their mainline binary blob might be good news for the Nouveau camp in general, but unfortunately at last attempt the reverse-engineered open-source support for this hardware that's about eight years old still comes up on the faulty end. The only GeForce 6 series hardware I still have around are GeForce 6600 GTs and when last trying them with the latest Nouveau Git a few months back they were still in a regressed, unstable state.
(Of course, for those following @MichaelLarabel on Twitter, this news post shouldn't come as a total surprise.)