Google Panda 4.2 was released in mid/late July 2015 and Google promised us it would roll out over "several months." So 4.2 started around July 18th, which was less than two months ago, about seven weeks ago.
There is no way it has been fully rolled out because it hasn't even been a couple months yet, let alone a few or several and Google said several.
But someone asked Google's John Mueller if it is done rolling out in a Google+ hangout yesterday. John wasn't able to answer the question because he didn't know. But he did address it at the 43 minute mark:
Has the latest Panda fully rolled out?
I don’t know. I tried to check before the hangout but I didn’t receive an answer there yet. I don’t know. I don’t have any full answer for you there.
From the information I have, I am fairly certain this has not been fully rolled out yet.
Learn more about the Panda update over here.
Forum discussion at Google+.
