Siri was appeared when iPhone 4s came to the market at 2011. But since 2011 siri has no any major updates. I dont know why apple dont finish they product. Siri has big potential but aplle "forget" about it
I think the problem is that if you try to make Siri look too "smart" then users will try to do even "smarter" things, assuming that Siri can understand. They then get frustrated or disappointed when it doesn't work.
One thing I'd find useful is if Siri could ask you for spelling clarification when it doesn't quite understand. "I didn't recognize the name of what you are searching for -- could you spell it for me please?"