Bankers can not influence the situation with bitcoin. Bankers can take an unlimited amount of Fiat money, but to have access to bitcoin they can't. Besides who wants to borrow in bitcoins if the price can rise to it. Such a loan can result in bankruptcy.
Currently I doubt if anyone will borrow in bitcoins because if the upward trend but the opposite holds true too, you can also borrow and pay less if Bitcoin prices goes down.
Agreed, but both increase and decrease is not that assured to take place at certain time gap. It all happensin a gradual manner based on the incoming user base and the inflow of investment into it. So bankers doesn't have any role in it to play.