Well it's not really a new design exactly. Rumors have been building up the last few months that MacBook Pro are going to go to the Air form factor and lose the optical drive. So there will be just one MacBook line of 11'-17' inch screens with super thin design. I suspect it will warrent a mention and be shown at another conference, likely at WWDC since due to the Ivy Bridge processor the Mac refresh will be in the summer which times it perfectly with WWDC and Apple likes limiting the conferences they do to a handful a year. The focus of the WWDC conference will be the new iOS revision like it has been the last few years though.
So it's new for Pro but not really new, since we seen the design in the 11 & 13 inch airs. Apple is already building to this, they only show Airs anymore in any press images that involve MacBooks.
Basically I see it going as
March: iPad 3 reveal (with new Apple TV as the bonus)
June: WWDC conference showing off iOS 6 (with some on Mountain Lion and refreshed Macs coming out that summer as the bonus)
Fall: New iPhone reveal with some more iOS 6 information (and some talk on new iPods as the bonus)
So it's new for Pro but not really new, since we seen the design in the 11 & 13 inch airs. Apple is already building to this, they only show Airs anymore in any press images that involve MacBooks.
Basically I see it going as
March: iPad 3 reveal (with new Apple TV as the bonus)
June: WWDC conference showing off iOS 6 (with some on Mountain Lion and refreshed Macs coming out that summer as the bonus)
Fall: New iPhone reveal with some more iOS 6 information (and some talk on new iPods as the bonus)