Don't they need Whatsapp though to get messages from others that use it? The network effect is strong and it is unlikely someone can make an orders to magnitude improvement on messaging software the compels people to switch. Barring major missteps they can be reasonably sure to keep a hold on the market.
Hmm. I started messaging using ICQ, then probably Yahoo, then microsoft messenger, now it's Skype. The first three offered exactly the same service. The other day I tried to convince someone to contact me on Whatsapp but he has already Viber. The network effect doesn't seem to be that strong, and sudden, catastrophic network switches happen all the time.
