Nope, this is just conspiracy theory and I don't believe any of it.
Siri is proof otherwise. They rushed Siri to market.
Edit: and it's not putting all of your eggs in one basket. There are always projects incubating at different stages. They have schedules and planned release dates to coincide with certain models. There are probably projects in progress now that won't be ready until 2013 and others in 2014. Sometimes they slip. this is how it works at most companies. But if you think they hold them back just to sell them in the next model, you're just buying into a buch of conspiracy theory bunk.
Not conspiracy theory bro, just business.