The ideal silicon solution is a system-on-a-chip (SoC) maybe accompanied by an external graphics co-processor (if it's not already integrated). For ARM architectures, that basically means 1 or 2 chips to power the entire computer versus Intel's 3, 4, 5, etc. Peripheral devices aside, ARM architectures use an order of magnitude less power than equivalent Intel architectures. What that means, is that the computers we use for our daily tasks, including document / internet activities, multimedia, programming, numerical analysis, etc, will have no fan, no heat-sink, and enough battery power for 10 times the active computing or standby time as Intel-based devices.
Now, I came across an article that I think actually has some merit. Apple could potentially become the next big-time ARM licensee and chip fabricator! Considering their recent acquisition of P.A. Semi and their huge successes with the iPod and iPhone (both ARM devices), they would technically stand to save millions by designing and fabricating their ARM chips in-house rather than purchasing them from outside vendors. Now in terms of porting the OS X to an ARM device - piece of cake. The core of the Apple operating system was designed from the start with portability and inheritance in mind. Their software is already pre-built and packaged in a universal binary format. With all likelihood, all they would need to do is highlight a check-box in XCode to build OS X for the ARM.
Honestly, I've never owned any apple products other than a second-hand 4th generation iPod that I lost on my last flight, mainly due to the prices, but if Apple decides to make a competitive move in the netbook market, then such a device might be the first Apple computer that I would buy, if the price is right.
To elaborate - I'm a really big fan of the TouchBook from Always Innovating, Inc, especially with the detachable keyboard, and touchscreen / tablet form factor. If Apple could do the same, with a unibody aluminum case, have nice illuminated keys, and throw in that always-on 3G HSDPA modem that Qualcomm has in their Snapdragon, then I would be 100% in. In that case, I would very likely be willing to cough up another hundred for what I see as the ideal netbook. Of course, this could draw the power ratio to something like 1/7 instead of 1/10 when compared to an Intel netbook, but that still makes a very, very big difference.
On a final note, in 2010 consumers will see the dawn of when ARM chips actually incorporate two applications processors (aside from radio, DSP, Graphics, etc), much like the 'Core Duo' from Intel. Apple could incorporate two ARM cores, in order to retain that same UI responsiveness that Apple has been so well known for in the past.
Below is a block diagram [via Engadget] of the new ARM Cortex A9 chips that will begin to appear in 2010. The Cortex line of ARM processors was a step in a slightly different direction, being the first ARM devices to support out-of-order execution (OoOE), and although ARM chips have supported single-instruction-multiple-data (SIMD) since the v6 instruction set was introduced, OoOE will boost ARM performance to a level closer to Intel processors, which have traditionally used both OoOE and SIMD (as MMX). OoOE represents instruction-level parallelism while SIMD represents data-level parellelism. It should be noted that both of the aforementioned optimizations are independent of each other as well as independent of instruction pipelining. However, having pipelining, OoOE, and SIMD on the same chip leads to a exponentially increased complexity, resulting in a very large and necessary amount of silicon to reduce data collisions. This is the primary reason that Intel chips have been had such a long history of being power-hungry. Hopefully, this won't have too large of an effect on the power efficiency of future ARM chips.