If you're still hanging onto the Google Talk app on your Windows PC, you might want to consider moving to Hangouts. Google's Product Manager for Google Voice and Hangouts, Mayur Kamat, took to Google Plus today to announce that, as of Feb. 23, the Google Talk app for Windows will be deprecated.
For some time now, our team has shared that we plan to focus our efforts on Hangouts. The Google Talk app for Windows will be deprecated on February 23, 2015. This will allow us to focus on bringing you the most robust and expressive communications experience with Google Hangouts.
While this doesn't mean that the Google Talk app will immediately stop working, it will stop receiving updates and could very well break in the future. On the bright side, however, Google Talk does support the Jabber protocol, so many third-party apps should continue to work. Regardless, now might be a good time to finally make the switch to Hangouts by using the Chrome app or Gmail.
Source: Matur Kamat (Google+)