Depends on how you define "new".
I would like to see - and would not be totally surprised to see - small refinements, in particular a MacBook-style latch (I'm not fond of the one on my PowerBook) and a user-upgradeable hard drive.
A totally new case though? I doubt it. Apple has, at this point, created a very specific design language for each of its product lines. And the MPB is the longest-standing of those, with a very clear family resemblance between the entire PB/MBP family from the original TiBook right through to today. The appearance of a pro Apple notebook has become a computing icon. Just like the Lenovo/IBM ThinkPad design, I expect Apple to stay with this aesthetic until some paradigm shift renders it totally obsolete, whether that is in 5, 10, 20 years or whatever.
Even the MacBook, whose case design was totally new, is clearly an evolution of the white iBook G3. Again, this is the appointed official "look" for a consumer Apple notebook.
The current iMac and Mac mini are probably pretty much aesthetically set in stone too, though the iMac has had the most major design changes (three) of the Second Jobs Era. (But then, one could argue that the original iMac design lasted, via the eMac, right up to the extinction of the CRT display, so the only "odd one out" was the LCD iMac G4.) The Mac mini design is clearly now the Appointed Official Apple Look for products of that size, having not only been appropriated for
tv but also with the AirPort Extreme having been redesigned to mimic it. This even extends to the AirPort Express's resemblance to every modern Apple notebook power adapter, and the Apple Remote with the original iPod shuffle.
And of course the iPod itself is iconic, though if we see the full-sized iPod become flash-based, it will be time for a major redesign. What will stay, of course, is the omnipresent click wheel - the iPod design signature.
And Apple's displays - well, this is what a modern display is supposed to look like; namely, a panel with the thinnest bezel and most unobtrusive stand possible. But then, everybody does that.
What's missing here? The Mac Pro! Not a design icon, IMHO. Minitowers are simply not sexy enough to really sink into the public consciousness. But I expect the current aesthetic to stick around, because it matches the look of the MacBook Pro, and
that is an icon. So there.