Anecdotal: my tight group of 12 tech-unsavvy friends very trepedatiously migrated to Signal after the terms update and I said I'm bailing on WhatsApp whether you're coming with me or not. As soon as the group came over, I got tons of "wow, I like Signal better!". Then the outage happened and I was worried, but everyone stayed and I strongly doubt will go back. Though some do keep WhatsApp for other friends, I think our litte migration will actually cascade into more.