Short answer - yes, you can 🙂
There seems to be some confusion between ACR and Adobe DNG converter. I just used the latest version of DNG converter (6.3) to convert Sony NEX raw files and opened them just fine on CS3. ACR, however, is a plugin, and the latest version will not work with older versions of PS. I would recommend downloading the free DNG converter and using CS4 rather than upgrading PS. I know it's an extra step in the workflow but for the price difference and the ability to try different converters using the DNG files that's gotta be the way to go.
Hope this helps
Scott