1. Fyi, once there was a similar thread like this:
2. Afaik, opening up the driver source might not be possible due to some IPR issues, licensed 3rd party code and so.
3. Afaik, NVIDIA was planning to, or even did, decrease the linux developer staff. This means that the guys who are left are loaded probably more and more.
Anyhow, probably there are much more developers working on Windows drivers. Considering that, the Linux driver situation is not too bad, IMHO.