What are the threats for financial system from bitcoin?
There aren't any.
Bitcoin isn't likely to replace fiat or compete with banks in student loan or house/car loan markets.
Bitcoin also isn't likely to be used in healthcare, real estate, manufacturing, tourism, pornography nor any of the big global markets of the world.
If anything bitcoin will have a positive effect on financial systems by giving them incentive to mirror or exceed bitcoin's stability & growth.
Hydrogen you are wrong my friend, bitcoin is used for all the things you mentioned. Bitcoin is replacing fiat, now you have alternative, you can gamble with fiat or with bitcoins, you can buy things with fiat or with bicoins. As you see bitcoin is taking part of profit, and with time that part is bigger and bigger. From their point of view bitcoin is taking more profit each year from them. Bitcoin, read blockchain, is competition to fiat system and threat for it. Future can bring many changes, and this battle will last for decades in my opinion.