According to JP wiki, DMM got an whole 12 himes added to gem gatcha 9 months after the first set, for a total of 24 total R's in their gem gatcha. We just that that first set added last event, or the event before that, I forgot, didn't pay attentions since I already had all of them beforehand. So early 2018 should be about right unless Nutaku decides to do it earlier.