Well, clearly then, the return to mining is an economic inefficiency that should tend to zero over the long term, that it does seems to be the consensus.
Mining may be a losing proposition for those who's costs are higher than average but that is no different than any other industry. There is no consensus that mining will trend to zero over the long run. Mining will always be profitable for those who costs are lower than the network average.
Besides, the mining capacity arms race results in equilibrium being a moving target. I seriously doubt most miners who make a hardware investment for that purpose at this point in time will ever reach break even before something better to do comes along.
Then wouldn't the prudent decision be to .... NOT make a hardware investment at this time at least not until ... something better comes along. The network likely is overcapacity at this point but that is no different than the auto industry being over capacity in 2008. Lower profitability will push out the least marginal miners. In time FPGA will make almost all GPU miners too marginal to continue mining just as GPU did to CPU miners.