I am starting to believe that over the past couple weeks that Google has begun to either push the Panda updates out more aggressively on a manual basis or has set it to roam free on it's own - in the wild.
Yes, I think that Panda is now a rolling update. I can be totally wrong, but based on reading the various threads in multiple forums, it seems like Panda is updating almost daily. Maybe it isn't Panda related but it is hard to tell.
Skim towards the last 30 or so posts in this WebmasterWorld thread.
Anyway, I do not have confirmation from Google on this, nor do I think I would get one. But no one would be surprised if Google did eventually make the Panda algorithm a rolling update of some sorts.
For more of our stories on Panda, see our Google Panda category.
Forum discussion at WebmasterWorld.
Update: So this is not a rolling update yet but Google did do a small Panda update as of late last week. I have official confirmation at Search Engine Land but here is the statement a Google spokesperson sent us:
We're continuing to iterate on our Panda algorithm as part of our commitment to returning high-quality sites to Google users. This most recent update is one of the roughly 500 changes we make to our ranking algorithms each year.