The best replacement for hipchat is slack.

The best alternatives to hipchat are rated as following:
★★★★★  slack
★★★★  campfire
★★★  irc
★★★  flowdock
★★★  yammer
★★  jabber
★★  kato
★★  groupme
★  lync
★  hall
  chatter
  openfire

Your alternative for hipchat is not listed? Suggest!
Speaking about hipchat, one probably shouldn't forget about adium.

Other search terms related to hipchat and their ratings are:
★★★★★ adium
You have in mind a companion for hipchat and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of hipchat in all years. Click on graph for more.
hipchat
slack
campfire