First, what's important to know about MACD is that, over time, it tends to revert back to the mean, or zero line. The farther the MACD gets stretched above or below the zero line, the more likely it becomes that the underlying asset it is measuring will reverse course. Since the monthly silver MACD is the lowest it's been in 20 years, the odds that it continues to decline from here are quite low. The odds are much better that it begins to move higher.
Secondly, we have just now seen a positive signal-line crossover (the black line has crossed above the red line - again, see the red circle). Without getting into the details, this means that a major trend reversal to the upside is now at hand. Look at this chart and you will see that major moves (both up and down) occurred after a signal-line crossover.
So how high will silver prices go? It's tough to say, but I'm confident that the move will be powerful and prolonged as we are coming out of deeply oversold territory. Based on the measured move from silver's recent breakout, I would expect to see new all-time highs in the not-too-distant future.