Pick one of the following options:
Option 1: Use the Latest Free DNG converter.
Have All Your Current Capabilities, But With An Extra Step for You To Perform.
You can download the latest Adobe DNG converter, which knows about the raw files your new camera produces and can convert them to DNG files your older version of Photoshop can open via the Camera Raw plug-in. This is not as integrated an approach as using all new software to go with your all-new camera, but it DOES make it possible for you to use your brand new camera in Raw mode and get exactly the same functionality out of your old Photoshop that you always did.
You would download and install the very latest version of the DNG Converter (6.4 at the moment) then whenever you want to edit raw images you'll go through a process something like this:
1. Upload the raw .NEF files from your camera into a folder on your hard drive.
2. Run the DNG Converter application and select the folder (it works on folders, not files).
3. Convert all the .NEF files to .DNG files.
4. Open the .DNG files into your current version of Photoshop through its Camera Raw dialog, which understands the DIgital Negative format.
Read How to Download Adobe DNG Converter for Windows
Read How to Download Adobe DNG Converter for Mac OS
Option 2: Upgrade to Photoshop CS5
New CS5 Capabilities, Full Integration, More Convnenience.
You can upgrade your Photoshop to the latest version, in which Camera Raw knows about the raw files your new camera produces and can open them directly. This gives you maximum integration with Bridge as well. And you get the new 2010 process for converting Raw files and new Photoshop CS5 features.
Read More About Photoshop Upgrade Information