Sure, it would be more work for them, but the people behind OGG Vorbis are keen on getting support, so I'm sure they would be more than happy to help. They already provide sample code, and may provide more than that, which means that Apple has a really easy job of adding the support.

It seems more likely that Apple would release, or someone will hack open, ways to add codec modules. I imagine that iPods already do codecs in a modular way, since it would make development a lot easier.

I might even buy one if I could play OGG and encode to Speex on the fly.