I hate to say anything negative about Bitcoin because it has done so much for my family, however one day when 90% of the Bitcoin has been mined the difficulty will be too much any many miners will give up mining. When the miners stop mining Bitcoin, the transfer fees will be very high and that will lead to the price tanking. If they have no contingency for this, it will be the "Bubble" that they are all calling for. However, Bitcoin is just the proof of concept, I think at that point another coin may take the number one spot I see Vert Coin filling this spot.