I think they're focusing more of their efforts on getting the iPhone right first, which is probably a good idea. They really need to have iOS 7 ready for the next iPhone next month, but they have more time for the next iPad. I wouldn't be surprised to see iOS 7 released only for iPhone at first, and then for iPad a few weeks later.
I am not fan of delaying...I hope they short things out before general availability. As iOS 7 is the mile stone for iOS, I think it is important they roll out for every devices out there as soon as possible.