With every new camera that is released, a new RAW file is created that requires updated software support. As a result, companies like Adobe must continue to update Lightroom, Photoshop etc to provide the ability to open these images. That means, if you do not upgrade, you will not be able to open any RAW images from a camera released after the version of Photoshop you have installed. Basically, a new camera also means upgrading to the latest versions of Adobe software.
This problem appeared a few weeks ago when a friend using an old version of Photoshop asked me why he couldn't open the RAW files of his new Canon Rebel. Instead of suggesting to spend $250 on upgrades, I asked him to try converting Canons .CR2 RAW files to .DNG (Adobes attempt to standardize the format) using Adobes free DNG converter. The converter is updated with every ACR update. Unless Adobe changes the DNG specification dramatically, any version of Photoshop should be able to open it. It worked in this case.
I personally convert all of my photos during import to Lightroom because I support the idea of having a consistent RAW format. More importantly, a .CR2 is read-only and I find it annoying that Lightroom or Photoshop creates a side card XMP file to record the changes. If it's a .DNG file, these changes can be written back to the .DNG RAW file eliminating the need for 2 files for every photo.