WhatsApp already implemented Axolotl - https://whispersystems.org/blog/whatsapp/

It's only used opportunistically, though (which is still much better than plaintext).

> Implying that opportunistic encryption is much better than plaintext

Unless you have an active attacker, in which case they are equivalent.

No security measure will 100% prevent attacks; any security measure is about increasing the cost to attackers. Forcing attackers to be active is a good thing on this measure (though of course if you can use a technique that is also effective against active attackers this is better still).

So, overall, much better :P

Nope. https://www.youtube.com/watch?v=ibF36Yyeehw

I said officially announced. Do you have a link from Whatsapp saying that?