Of course they're unattached. It's just another instant messenger. Or are people still loyal to ICQ, AIM, MSN Messenger...?
(Even worse, WhatsApp relies on teenagers. How many social circles endure beyond high school? Do you still IM people you knew back then... or even as recently as two years ago?)
Maybe adults will fall back on the best messenger based on technical merit (probably Hangouts?), but WhatsApp is neither sophisticated nor particularly appealing for the long term. I'll put down money that it'll be forgotten within the decade. What the hell was Facebook thinking?