In under 2 years? There has been many decades of development on this. I think Nuance is based off of earlier technology. I simply don't see Apple coming in and build it up from scratch with their own tech in such a short time. And like I stated, the real issue of Siri's usability and performance is based on the intelligence of the digital personal assistant, not the speech-to-text engine, so if they do that I'd expect that to happen well after Siri is well out of Beta and considerably more robust and more flawless.
No. I only meant they have had sufficient time to capture speech samples on which to base speech recognition algorithms.