NVIDIA will continue to maintain drivers for GeForce 6 and 7 series graphics cards till 2017. Earlier the company had decided to drop support for this series of drivers. According to this knowledge base article, 304.x series of drivers that provide support for most 6 and 7 series graphics cards will be maintained for compatibility with newer kernels and X server.

The 173 series of graphics drivers will be maintained till end 2013. This includes most GeForce 4 and 5 series graphics cards. However, its unlikely that 96 series graphics card will be ported to use the newly released X server 1.13. Users will have to switch to the open source Nouveau driver for this hardware.

You can read the knowledge base article here.