The Ghent Workgroup (GWG) has published their first specification for digital printing on cut sheet. The new Digital Print Specification is based on the GWG specifications 2015 for offset printing. Some requirements have been relaxed (e.g. overprinting) or lowered (e.g. minimal image resolutions). There is only one variant available for PDF/X-4 CMYK+RGB (images with ICC profiles allowed).
In the mean time the new Preflight Profiles for Digital Printing have been released.
PDFX-ready has already released a preflight profile for toner based digital printing in 2015. This is mostly identical to the new GWG specification.