Bitcoin trading volume: what's going on?
This question could be asked of any financial instrument. Volumes decreasing is not a bad or good sign. It's simply something that occurs when volatility decreases. The market theory behind it might go like this.. Price has fallen to such low points sellers are no longer interested in selling. Buyers are still hoping for lower prices. This effect causes the price to trade within a range where anytime the price rises to an acceptably high level sellers begin to sell again and any time it reaches an acceptably low level buyers begin to buy. As traders notice the price is range bound more traders stop trading. This compounds decreasing volumes and also decreases the trading range. Eventually this will lead to reduced trading interest which can then lead to the price breaking out of the range in the direction of least resistance (as traders give up their respective buying or selling).

Sorry there is no provable answer to your question, as this is all market theory. However, if you were to look at different financial instruments historical volumes you would see many instances similar to what is currently happening in bitcoin's market volumes. This is a common pattern in markets and is normally described as not predictive of future events (range trading is often thought as having a random breakout direction).

https://en.wikipedia.org/wiki/Triangle_%28chart_pattern%29#The_symmetrical_triangle