The comments here are rather bleak, but for me, this is fantastic.
My family is all on WhatsApp, but my friends and colleagues are on Messenger and SMS.
Previously, I would only ever use Messenger, checking SMS and WhatsApp once a month at best.
A while ago, SMS got integrated to Messenger, I started staying in touch with people who only use SMS.
Now that they're adding WhatsApp, I literally don't know a single person I can't reach from Messenger/Gmail.
I love it, and I hope things go smoothly.