Google's Gary Illyes did say they do have launch a date for Penguin 4.0 but John Mueller said this weekend on Twitter that they don't have any dates to announce around this Penguin update.
John said, "we don't have any dates to announce for that, sorry." This is in response to someone asking about the Penguin update. Here are those tweets:
We know it is soon, they are working on the announcement for the Penguin update. We also know they were close before and then gave up estimating its launch.
We are now less than one month away from it being the two year anniversary for Penguin 3.0 - the last real big Penguin update.
Forum discussion at Twitter.