This information applies to version(s): 1, 2, 3
This depends entirely on you, and on what you intend to do with your images. Keep in mind that a RAW file is THE original, and cannot be replaced.
On one hand, DNGs created by DxO PureRAW can be considered 'perfect' files, and if you are sure that you won't ever want to reprocess them, you could delete your RAWs.
On the other hand, many users have been so impressed with the high-quality results delivered by DxO DeepPRIME that they decided to reprocess their archived RAWs, many of which were taken over a decade ago.
The best idea may be to keep the original RAWs in case we eventually offer even greater improvements to our RAW processing. DxO PureRAW is going to evolve over time, and so are its denoising capabilities.