There is a big flaw in this assessment because the reduce in mining equipment sales does not mean that the interest in the market is going down, support for mining is one thing and investing in the coin itself is another aspect to look at the market, there is another aspect for the slow down in GPU sales simply because there are ASIC machines to mine those coins, so this is an inconclusive study.
The two are related. Without growing interest constantly pushing up the price, buying new GPUs and investing more money in mining is not going to pay off. So you would expect decreasing mining investment to portend or at the very least coincide with falling interest and falling price. It is only through the constantly increasing interest and support in Bitcoin by new buyers that the price can rise, and the price rise is the only thing that will make new investments in mining equipment profitable. You cannot make money buying more equipment to get a larger slice of the mining pie when prices are falling, the mining market is far too competitive for that.
