Gary Illyes from Google said on Twitter yesterday that this may be the last Penguin update. He said "it's likely there won't be next one," referring to the next Penguin update.
Here is the tweet:
We know the next Penguin algorithm should be the real time version and with real time algorithms, they don't get pushed out on occasion, instead, they run all the time. So new Penguin penalties and recoveries will happen all of the time.
This is similar to Google Panda updates where Google said we likely won't notice any more updates to them because it is more rolling. But truth is, we do notice small updates, not the drastic ones from the past. The thing is, Panda is rolling, Penguin should be very very quick, based on how quickly Google indexes new and old links.
In any event, I suspect that when Penguin 4.0 hits, we may see some changes rapidly over the next month or so and then once it is good enough, they will set it free and let is roam the fields as it sees fit.
Forum discussion at Twitter.