Converting proprietary raw files to DNG is just a conversion of the file formats; the actual contents are left alone. A DNG file is just as raw as the original raw file. All raw formats as well as DNG are just variants of the TIFF format anyway.
Many photographers convert to DNG without embedding the original raw, then archive the DNG and throw away the raw file. The only drawback of this approach: you cannot use the original manufacturer's raw converter anymore.
-- Olaf