It is worth noting that not all vulnerable addresses will be hacked at once, but rather, it will happen gradually over months or even years. There are a multitude of reason in which coins which are not lost may not move for long periods of times.
Which should in theory mitigate the effect of the short term price hit, due to panic, and the fact there's new coins being reintroduced to the economy. However, it likely means you'll see a smaller effect, for a longer time since they'll be gradually taken, and reintroduce rather than all at once.
Depending on your perspective, both scenarios have their pros, and cons. Ultimately, the very long term probably isn't effected.