Here is the official statement from Steinberg about the new licensing system. They haven’t communicated any date when it will be introduced. There are, however, some rumors and speculations in the Dorico forum that it might be coming together with the Dorico 4 update expected later this year.
According to the available information, the system doesn’t require a dongle any longer, i.e. it’s entirely software-based. I’m not sure if it needs an Internet connection to frequently check the validity of the license. This would definitely be a problem with many studio computers that are not connected to the Internet.