Siri technology is about 10-20 yrs away from being major
Siri technology is as close as how much money you're willing to throw at integration today.
It's really a simple matter of building APIs into all the services Siri needs, which could be accomplished in months, not years, and then expose those APIs to the internal Siri engine.
It's more a matter of time and resources than anything else, if the backend integration picks up steam, Siri could be a SIRIous force in no time at all.
The fact that Apple acquired them could mean either massive resources are now being thrown on the project to make it happen as quickly as possible... OR ... it's about to be muddled down in so much corporate quagmire that it will suffer a major falter and allow competitors to quickly catch up and bypass it's current status.
However, it won't take 10-20 years to make it major, if it ever becomes major, it'll happen much sooner than that, the technology is all here if there's enough money to make it happen and Apple has boatloads of cash so if anyone can do it, they can.