I don't believe that DPP modifies the RAW file as I can undo my edits to the RAW, and LR does not see those edits when I import those RAW files. What I'm wondering is, is RAW + XMP future safe? I'm sure Lightroom will always be able to read those files but is DNG better?

I keep a copy of my RAW file and DNG files plus my JPG. Keeping both DNG and RAW really takes up space but I don't want to get rid of the RAWs, just incase.