Bounty won't disappear unless ICO disappear. Few projects have ICO on exchange and hundreds projects don't.
Sooner or later ICOs will be gone because that's where most of the scam coin came from.
Question is, how much impact bounty hunters have and where investors are finding projects, here, on rating sites or somewhere else.
Bounty hunters are spammers from social media to message app and even emails. From those spam, investors are finding the project of an ICO.