Coming around the 5 year anniversary, DUSK HD is going to be a big full visual remaster of the very popular shooter so here's what they've said about it.
It's a free update that will update everything including enemies, weapons, all models, textures — everything they say will be improved. Around Halloween we can expect to get a trailer showcasing an on / off comparison, with a full launch along with their modding SDK and Steam Workshop support around the 5 year anniversary which would be December 10th.
The good news is that it will be entirely optional as the HD content will be available via the Steam Workshop as free downloads so you can keep it as it is if you prefer it. You'll be able to use the old or new HD assets for modding too and upload your own creations.