I dont expect bitcoin to ever become a world currency but i dont think the miners are going to stop anytime soon, i actually do wonder sometimes if its just me and a few other people that use bitcoin since no one i ever speak to in real life have ever used it but the market cap shows that theres a few quid in it. You may think its low but it wouldnt take much to make that rise massively.
I don't think so, if the bitcoin's currency continue it's actual success i believe that it can become a worldwide currency used everywhere easily, especially with it's simple and easy to use features.
There are a lot of variables in a statement such as Bitcoin becoming a worldwide currency, some of it being what the definition of a worldwide currency is, some of it being whether or not Bitcoin can figure out a way to get quick transactions, and a simpler form of wallet design so that the average person can grasp it easier. Long strings of alpha-numeric characters are confusing when it comes to someone, and so a wallet design that allows for names or other forms of ID masking the actual address of the user would be great for mainstream adoption.