Is a new found exploit going to kill Bitcoin?  Possibly.

Yet, in 2010 somebody was able to find a bug good enough to produce 184 BILLION BITCOINS for themselves.  Did Bitcoin die?  No, a solution was found and the problem was eventually solved.

This is what I expect will happen to Bitcoin in the event of a Quantum Computer powerful enough to 'kill Bitcoin'.  A solution will be found and we will simply move on after a few minutes, hours or days of panic.  That is it.