I don't think you really understand what I was talking about, and I'm going to go out on a limb and guess that you're an ESL (English Second Language) poster.
So, with that in mind, let me try to explain this to you in a bit more simple terms, so that we'll be more likely to reach some kind of common point. When I speak of modular graphics, you wouldn't be gaining in physical maximum resolution because the dot pitch of the actual LCD wouldn't change, but that doesn't mean you shouldn't use faster GPU cores. For example, I have a CRT on my desk in the other room that's now hooked up to a dual 1.8 G5 with a 9600XT. It used to be hooked up to a single 1.4 G4 with a GeForce 3, and now it's very, very much faster and better at redrawing the screeen even though the physical monitor I use hasn't changed.
If the PowerBook were to incorporate something similar to what Alienware is doing with the modular PCI graphics cards in laptops, you could speed up your performance without buying a new machine. If you think your graphics are too slow, you'd buy a new card and remove the old one from the machine so that you could slot in the replacement. It's just like what you do with upgrading a desktop machine, only it's starting to be possible in portables.
Does that make it clearer?
For the most part, 64-bit computing is really only beneficial to the scientific and engineering community. They use enough specialized, high-end systems and math that the investment is worth it in terms of memory (using more than 4GB per process) and the overhead for using larger pointers. Also, since they're likely to use integers that are 64 bits, it saves them and makes things more efficient because they're not carrying out two 32-bit operations in the place of one 64-bit.
This is unlikely to be true in the consumer space for some time, but the bitness of processors is being used as a way to push the update cycle while the gigahertz race flattens out.
I could be mistaken about the implementation in Tiger, but database-driven file systems have been done long before 64-bit addressing was really an issue. The reason that Spotlight works the way it does is thanks to a database and the journaled file system, which work together to have fast pointers to the location of multiple kinds of data. Instead of searching the entire hard drive, it merely scans the table.
Thus, it has nothing to do with the chip or the OS, per se.
The shell is the least of Apple's worries, in this case. Everything you just dismissed as secondary is the primary concern when designed a professional system - processor, storage, and I/O. Especially in the case of a laptop, you need something power efficient, since power efficiency leads to heat efficiency, which in turn leads to a lessened need for cooling. This is one reason that Apple has stuck with the G4 for so long, and why Intel moved to the Pentium-M for their high-end portables.
A fast, efficient 32-bit processor will be better for a portable than a 64-bit one that's far hotter at lower clocks. It's that simple, unless there's something really bizarre done with the design.
