The problem will likely be the flood of L3's coming online and the massive increase in difficulty.  Profitability is likely going to get squeezed pretty hard here. I am trying not to be negative, but I think we have already seen the precursor with the big spike recently that we thought was the A4's.  Most likely that was due to the L3's and not as much the A4's.  Just a wild guess on my part, but it certainly fits the time line.  Not sure that these miners will be profitable for very long.