I suspect this will be painful to Twilio in a couple years. If you think anything like WeChat and its service ecosystem is coming to the rest of the world, it's going to happen on Facebook (or Telegram), not WhatsApp.
And again, if you look at what WeChat has done with embedded services, and believe that will spread, then you wonder whether it will happen on WhatsApp vs. something else. And I don't see Facebook putting the energy into the automation/interaction platform on WhatsApp that it is going to do on Facebook.
I thought about modifying it to include Asian saturation, but I was thinking more so about Facebook services, of which Viber is not one but an underdog