I say that anyone who invested some serious amount of money into ASIC's took and ACCEPTED the risk that in one day, his or her bunch of arrays of ASIC equipment might or will become obsolete, Inefficient or worse a bunch of paper weights in the event that the difficulty becomes so great, in the event that changes are made that affect mining performance and ultimately in the event that a big change such as from POW to POS completely renders your ASICs into paper weights and even then, you might consider your ASIC to be a "paper weight" but the truth of the matter is that you can go to coinwarz com website and see a whole bunch of SHA256 altcoins in existence that you can immediately switch to, continue to generate profits, hell even start a pump and dump campaign or organized campaign to get your target coin priced up while you are mining them and then sell them to bitcoin, ICN, Ripple, lisk, eth, INCNT or anything that actually hold its value.

See? Your array of ASIC equipment will never become paper weights.