I don't have any inside scoop here, but a huge partnership between Apple and Intel and an ARM-based iPad are not mutually exclusive. Most people acknowledge that, to get the kind of energy efficiency and battery life that people are starting to expect in mobile devices, current x86 parts are not a good solution. Nonetheless, we are stuck with x86 for anything that wants to run most existing desktop/laptop software until we come up with a virtualization, cross-compilation, or binary translation scheme that is efficient enough.

If Apple wants to continue selling Mac Pros and Macbooks, they will probably stay Intel for some time. Until Intel comes out with a part that can get Apple anywhere close to the many hours or even days they require for their mobile devices, Apple has no choice but to look elsewhere, and I can't see that as a reason to end a partnership on desktop/laptop processors.

Do you remember when some Intel Execs trashed the ARM chips, as used in iPhone and iPads, as not being able to handle "the real internet" (Intel code for Flash support).

Apple got a public apology acknowledging that Intels chips couldn't hold a candle to ARMs in this area:

http://news.cnet.com/8301-13579_3-10074228-37.html

So it seems like they're happy to keep Apple sweet as long as they use the Intel chips in the appropriate devices.

The "system on a chip" Atom CPU is still under development and needs a lot of work (ie. time), whereas ARM is here today.