I wouldn't count the 5 films thing as concrete just yet. Katzenburg said that he'd like to make 5 Kung Fu Panda movies, not that there would definitely be 5.
Of course, when the Suits in Hollywood get those dollar signs in their eyes, anything's possible.
The first Shrek was terrific; the second one was just trotted out to make some more cash, but it at least had its' moments. The third one was a total waste of time, as was that Christmas special. Shrek is a soulless shell of a franchise now; every new thing they do with Shrek screams, "We're only in it for the money!"