According to 9to5mac, early builds of OS X 10.9, which are currently tested, show that Maps and Siri integration may come to Macs next year.
However, it is currently unknown if Siri will be part of OS X 10.9 for users. Apple already offers Mac users Text-to-Speech and Dictation functionality, but integration with Siri would presumably offer voice search and voice command services to Mac users.