I hope the govt sees the reliance on this service and does something positive about it (for example, build their own or tie up with some company). Such massive dependence on a company with no contracts is going to end up in a mess later.
If for some reason WhatsApp suddenly vanished, people would switch to the competitors, like Telegram, Messenger, Viber, etc.
There would be chaos during the change, but that's just because the change happens suddenly. If it happens slowly (if the government continues to block WhatsApp, people will rely on an alternative), then I see no harm.
(It also failed; as of 2014, .doc was still used more than .odt by orders of magnitude in the major institutions - Commission, Council and Parliament)
Do we really have democratic nations that would rather rely on some corporation than the government? Is brazil such a nation. That is semi-alarming to me.