It seems unlikely they'd bring the encryption in. I often have several messengers open. My phone, my tablet, my home desktop, my home laptop, my other home laptop, my work desktop, my work laptop. How will encrypting like Whatsapp keep that working? Some how they'll always be tunneling to my phone from all the various machines?

Also, as an alternative, Hangouts stores my chat history in gmail (opt in), so unlike Messenger/Line/Whatsapp I have a history of all my chats on Hangouts which I actually find very useful.

That said, 99% of my friends and family are on FB Messenger