Hangouts isn't being killed, it'll be slowly transitioned to be more of an enterprise tool, similar to Slack and Skype. That won't mean it can't be used by consumers, it just means that future functionality will be tooled with different purposes in mind. Allo and Duo for the short term will work along side Hangouts and in the long term much of the functionality of Hangouts will be replaced by those two apps. Still no word on a desktop app for either though, which is one of Hangouts' main draws for me.