NVIDIA's Release 340.xx GPU drivers for Windows will be the last to contain "enhancements and optimizations" for users with video cards based on architectures before Fermi. While NVIDIA will provided some extended support for 340.xx (and earlier) drivers until April 1st, 2016, they will not be able to install Release 343.xx (or later) drivers. Release 343 will only support Fermi, Kepler, and Maxwell-based GPUs.
The company has a large table on their CustHelp website filled with product models that are pining for the fjords. In short, if the model is 400-series or higher (except the GeForce 405) then it is still fully supported. If you do have the GeForce 405, or anything 300-series and prior, then GeForce Release 340.xx drivers will be the end of the line for you.
As for speculation, Fermi was the first modern GPU architecture for NVIDIA. It transitioned to standards-based (IEEE 754, etc.) data structures, introduced L1 and L2 cache, and so forth. From our DirectX 12 live blog, we also noticed that the new graphics API will, likewise, begin support at Fermi. It feels to me that NVIDIA, like Microsoft, wants to shed the transition period and work on developing a platform built around that baseline.
Overall it sucks that they
Overall it sucks that they are doing this. Due to the way their drivers work, you cannot have 2 different installs, this means that the dropping of the old cards from the unified driver line will prevent users from being able to use their older cards along side of their newer ones.
This means no more dedicating an older card for physx, or running an additional display on the other card which is often needed if you run many full screen hardware accelerated games. (often if 2+ displays are sharing 1 card, when a full screen game is launched, you will lose hardware acceleration on the video playing on the other display. In cases like this, if you are playing hardware accelerated video in VLC player, it will often go black or crash once you launch a game in full screen.
Overall, there are many benefits to using an older card for additional displays. by killing off the driver line, users get stuck with either not updating their new cards, or losing the ability to run both cards at the same time.
I can understand nvidia wanting to drop older hardware, but what I can’t accept is their policy of preventing 2 different drivers from working at the same time, and thus you cannot install the old drivers for the old card, and the new drivers for the new card.