and mining and meeting recently the bitcoin and watching the boost it currently has many questions arise about the stability of the currency in the short or long term , but with the release of new ASICs and power of hash, and my questions are as follows .

If I assume that when you start distributing the new ASIC in a theoretical case to see that a millionaire is a good investment decides to spend about 5 million in equipment for mining, or suppose a government or banking group decides to try to boycott the bitcoin decided to invest a few million to acquire or manufacture equipment for mining massive , and maintain control of the currency , it could be the case that people who have invested hundreds or thousands of dollars in new equipment , the next day by the ability to earn 0.0001 acquired by the above that absolute produscan lost them ?

And my second question is: what is the formula to calculate the difficulty of bitcoins if you reach a certain amount of hash in mining?
I wanted to reflect on the bitcoin difficulty, that maybe is silly, because this fashion the theme of attack of 51% or selfish miners

     What if a change in difficulty as you are and the remaining 2000 blocks to undermine with a difficulty of 700 million the price of bitcoin is desplomase such levels that most of the hasrate abandon the network that was not profitably mined, imagine that he would tarry hastrate to 10% of the current, the difficulty really 700 million would thus undermine cost 10 times a block which would give an average of 100 minutes per block, little discouraging that hasrate quedase network and creating more currency in which no serious vicious cycle of declining hash mined.
What do you think of this? Maybe I miss something and this is impossible.