Pew slants LEFT. They're covering for the left, and trying to get us to lower our guard. Although there might be some truth--perhaps immigration is slowing--it certainly hasn't stopped.
I've seen a number of Pew polls that paint overly rosy pictures of social problems. They're quite often wrong, but by then, they've got another statistical report out on another subject, and the public (and watchdog media--what a joke!) have already forgotten about it all.