It is way too early to say that bounty will end in two or three years time, even five is tad too early. ICOs will still continue to exist as there are even more people or groups that show interest in cryptocurrency, hence, people will invest. And so long as ICO's exist promotion program will follow, and o will bounty hunting.
If and when ICOs stop promoting, or promotion program cease to exist, then so will bounty. But for now, I think it will for the 10 years.