It might do well, but it could also easily be a flop (as many other social initiatives from Google have been). Either way it's a long ways from catching up to WeChat, Viber, or even Facebook Messenger.
Hangouts didn't catch on because it was delivered as a group video calling service that then also did (or perhaps became about?) text, even becoming the default SMS app on Android.
It also hasn't caught on because it is overly complex. With any other video calling service you call a person and they have a conversation with you - of you initiate a group conference and off you go.
Hangout needs you to invite someone, but then what - you're still having this video broadcast by yourself? Actually, is it a broadcast? Can other people just join in? Apparently they could depending on your settings (in the past), but not this seems to have been separated to 'Hangouts On Air'? Who knows, I don't see why I should bother looking into it when there are clearer options available.
I love me some Google, so don't misunderstand me, and Duo is a big step in the right direction for the average users experience compared to Hangouts.