Gchat is officially dead, long live Hangouts
Gchat, or Gtalk, users have been served numerous prompts in the last couple of months, which warned them about the change and invited them to switch to Hangouts by the end of June. If you haven't done that yet, after June 26, Gchat users will be automatically transitioned to Hangouts.
Also, the Gchat app on Android will stop functioning, so there's no point in trying to continue to use it. Hangouts promises advanced improvements over Gchat, including group video calling and full integration with other Google services, so there's really no reason to live in the past.
source: Google
Things that are NOT allowed: