I know that updating the MBP now and then having a new one three months later is stupid, but I see it by the point of view of adding another laptop line.
As I already said, maybe Apple will silent update the Pro now, then at WWDC introduce a completely new Air, with new moniker too.
The new Air is actually the new Macbook. Just that they refreshed Air once more, but if they add some more ports to nMB as they did with the first Air, the actual Air won't have any more reasons to exist. I mean, why making a new Mac line (that was ditched 8 years ago because of Air) if it isn't to replace the Air role?
That said, a complete redesign of MBP has much more sense. A redesign now in March or in the fall? I don't know, but definitely they won't prior Air over MBP.