But, I've got some ideas about what's in the 3DS, based on the rumors that are out there, and what is known about both it and previous DSes.
Let's start off with what we know about previous DSes.
The original DS and DS Lite use a 67 MHz ARM9, a 33 MHz ARM7 (for sound and (when underclocked to 16 MHz) GBA compatibility,) two GBA-like 2D cores, and a primitive 3D core capable of 2048 polygons per frame, or 122,880 polygons per second.
The DSi clocks the ARM9 up to 133 MHz, although when running DS or DS Lite software, I believe underclocks it back down to 67 MHz. Also, allegedly, the ARM7 runs at 67 MHz when in DSi mode. Otherwise, it's pretty much the same story as before - basically, a twice-as-fast DS.
Also, based on overclocking experiments that have been performed, the DS family appears to require timing exact execution. Newer ARM CPUs usually aren't timing exact with older ones.
Now, for what we know about the 3DS...
It's backwards compatible with the DS and DSi. Therefore, it must have an ARM7 capable of running at 33 (and possibly 67) MHz, and an ARM9 capable of running at 67 and 133 MHz. Also, it will presumably have the old graphics hardware present for compatibility.
The GPU has been confirmed as the Digital Media Professionals Pica200.
So, let's get into pure speculation now.
An ARM11, at first glance, would be a logical choice for Nintendo. Fast enough, fairly cheap, and fairly low power. (CPUs such as the Cortex-A8 are too large and power-hungry for this job.)
However, the problem with an ARM11 is backwards compatibility. You're not running old DS/DSi code on it, so you've gotta have the ARM9 around anyway.
ARM9s scale to 533 MHz and beyond just fine, and they're even smaller and lower power. Which leads into... I believe the 3DS has an ARM9 as its main CPU, clocked at somewhere between 266 and 400 MHz (for low power consumption.) It will also have the ARM7 as a coprocessor, likely clocked at 67 MHz (unless the DSi only runs its ARM7 at 33 MHz, in which case I predict it will stay at 33 MHz.) The ARM7 does scale to 133 MHz, but given the functions that the ARM7 performs, I think additional speed won't be taken advantage of, and will just increase power consumption.
If I'm wrong, however, Nintendo could be doing something interesting with the ARM9 - for instance, running the wifi stack on it during games, or using it as a second CPU to offload tasks to. Nintendo has had a history of doing this with their handheld consoles - the GBA used the GBZ80 (which was present for 8-bit Game Boy compatibility) for additional sound capabilities, and the ARM7 in the DS did double-duty as well. I do, however, believe that the main CPU would be an ARM11 or maybe a Cortex-A5, though, if Nintendo went that route.
So, in summary...
- The 3DS will have an ARM7, likely at 67 MHz, and an ARM9 of at least 133 MHz (speculation, but required due to DS/DSi backwards compatibility)
- The 3DS will have a GPU based on the DMP Pica200
- Due to the CPU requirements, I personally believe that the 3DS will use a higher clocked ARM9, rather than moving to another processor, to save cost and power consumption
- If I'm wrong about that, the 3DS will likely offload some functions to the ARM9 while in 3DS mode, and use an ARM11 or Cortex-A5 as the main CPU