I'd pick a different classification. It's more like these groups:
1. Uses whatsapp out of momentum. Doesn't want to use anything else, but might if people really push them; i.e. open to transition to group 2.
2. Will use whatever. Some people in this group want to stop using whatsapp, but won't break contacts to do so. Some people in this group would prefer to stick with whatsapp to avoid the burden of a switch, but won't break contacts to do so. This is the vast majority of switchers.
3. Die hard whatsapp users. Simply refuse to switch to another app, because it's a hassle, and/or because they begrudge other people making a mountain out of a molehill and asking them to do anything. Might oppose yet-another-app; or might actually want to stick to whatsapp because they actually like the simplicity of the network effect.
4. Die hard non-whatsapp (likely signal?) users. Refuse to use whatsapp, likely due to privacy concerns or distrust of facebook.
I don't think most people trying to switch away from whatsapp are in 4. Anecdotally, I people I know asking to switch are clearly in 2, and are largely losing to those in 3. Only 1 person I know claims to be in 4, but I'm not really sure that'll stick if the exodus doesn't keep momentum. Because of the existance of the bulk of humanity which barely cares about this, and some of which will get annoyed at the suggestion - I suspect group 3 is much, much larger than 4, and that suggests this exodus will fall flat. The only real chance here is that since this is all about closed groups that network effects aren't so huge, so a considerable exodus without actual terminal velocity is possible.