I think it's a good move, and one that I've actually thought they should have tried long before this.
imo, KP was a brilliant batsman 2005-2007 and has been pretty mediocre since then. I feel the no.4 was no more than a ego position for him, it's where good batsmen play, but he wasn't really very suited to the position but perhaps wasn't quite gutsy enough to be first one in at 3, and too full of himself to sit at 5 for his career. This position puts more onus on him to deliver meaningful score but as opener he will always be in an attacking situation.
My only reservation is this move made far more sense when morgan was in the line-up. They are now without much firepower in the middle to lower order, they'd be as well taking the batting powerplay instantly if he's still in.