Apple has a huge headstart with Siri because it's already out now in beta form, and so Apple has access to real-world usage data. By the time Majel comes out, Siri will be even more advanced and will have been shaped by its users. It will be interesting to see how Google competes.
I think you're forgetting about the work Google has been doing for years now with Google Voice transcription, voice search, and the text to speech and back again translation products they have.
If anyone can take on Apple in natural language processing, I think it's Google.