I would love to see them return to black polycarbonate. Maybe titanium or magnesium reinforced on the corners with supports cast right into the poly. Then put in a true 16:9 display for killer presentations. I wouldn't care if it was two feet wide! And I wouldn't WANT it an inch thick, unless it were milled out of solid aluminum, because I want to use it in the bump-scratch-and-drop real world, not the land of "esoteric design utopia" where laptops are never dropped, bumped, twisted, scratched, handed from one person to another, or even touched.
I hear the Japanese don't like TiBooks because they are too wide to comforably use on their subway trains. I say give them 12" iBooks w/processing abilities at TiBook levels. For the travelling film/graphic arts/web design professional, however, give us a big platform, durable, versatile machine again. EXPANSION BAYS! Yes, you can hook up peripherals via FW all you want, but I don't want to bring an octopus to a presentation. I would rather hot-swap whatever I'll need (CDR-DVDR, extra battery, extra HD, etc) ten minutes before the meeting and have an elegant platform to work from.
Take a Pismo and just add about three inches of width to the case and the screen, 1.5" per sidethink 17" iMac widescreen display on a laptop. Make room for 2 G4 processors, 2 gig RAM, and true DDR RAM with 133mhz bus speed. Use the extra space to make BIG expansion bays for long battery life, huge auxiliary HDs, SuperDrives, etc. Keep the excellent output options, plus an additional DV out for Apple external displays (not that you'd need one) and perhaps two completely discreet FireWire busses instead of two ports on the same bus. Reinforce the chassis w/titanium or magnesium supports and gel-suspend a g-force resistant internal HD for hard portable usage. Offer a CardBus expansion chassis like the Magma only classier-looking and Apple-branded as a BTO option for use with PCI cards. None of this would be cutting-edge technology--its all here now.
The Apple G4 SuperPismonow THAT would be worth $4000 in a portable. Imagine the crowd that would gather around it at any CompUSA in the nation with that 17" screen! It would make the biggest Vaio look like a Timex Sinclair!
I say if you're gonna be a bear, be a grizzly... Make a statement... Over the top...