No one knows, and don't let anyone convince you otherwise. All we know is that silver is at 5 year lows.
5 year lows aren't that low though. In US dollars at least. If you wanted to be absolutely confident you were getting in on a bottom, you'd buy at the 2008 low. Gold and Silver both aren't at that level yet. If gold and silver goes below that point and stays there long term, we've all made a big mistake in anticipating inflation. We have the AUD to contend with as well, the low in 2008 for silver in the AUD was $13.13 or thereabouts.
Who says the 5 year low isn't the lowest it will go in a long term trend? It's simply a statement of fact, we are at a 5 year low. However you interpret the future is up to the individual. There is no such absolute confidence, except with hindsight. Why? What's so special about 2008? Is it the temporal junction point of the entire space-time continuum? Why can't the future price drop below 2008 levels? Who says it can't?