Bitcoin Death Spiral?

I've been skeptical about the value of Bitcoin almost since the beginning of its success. There are just too many problems with it to make it a stable, long-term investment. My biggest concern isn't the instability that the cryptocurrency markets have demonstrated; it's the energy requirements to mine Bitcoins and the every increasing size of the distributed ledger. Now it seems that Bitcoin may be entering a death spiral as the value decreases below the cost of mining it.

Yet the cost of mining bitcoin is not a fixed-dollar amount. There is a feedback mechanism in mining any commodity that applies to bitcoin: as the price of bitcoin increases, new miners enter the market, increasing the effort required to mine a bitcoin, as its reward will be shared among a larger group of miners. Similarly, when the price of bitcoin falls and miners exit, the cost of mining decreases. However, the number of miners cannot fall below a certain level, because without the miners providing the computing power to maintain the ledger, the bitcoin blockchain will not remain viable.

Mining at a cost higher than the cost at which you can sell in the futures market destroys value. So, any rational investor — even one who strongly believes the price of bitcoin will rebound — has no incentive to mine if the cost of mining is higher than the future price and is better off buying in the futures market. And unlike gold, which can retain its value even if mining activity stops, bitcoin can have no value absent the mining activity that maintains the ledger of who owns it. Absent the mining activity, bitcoin is a just a set of encrypted numbers with no value.

Update: I meant to mention this and forgot to - the energy cost of mining Bitcoin. According to this Wired article, Bitcoin mining now uses more energy than the country of Serbia. Obviously, this is not good.