Bitcoin is definatly worth investing in and is here to stay, i reckon bitcoin will be in the 6 figure region within 20 years.
I am not sure It will be 3 or 6 figure But sure It only rule the world currencies and It will be familiar to all the people in the world Because Its digitization, Value among the other currencies will make their future people choice and Bitcoin is worth and best decision for the who are all saving the bitcoin as long term goal.
the price figure really doesn't matter. even I think if bitcoin price reach to 6 figure mark(which is not gonna happen) then the usage of bitcoin will probably reduce to a lower base. people using bitcoin and new people coming to use bitcoin because bitcoin have a good price and everyone can afford it. price can go to 4 figure but 6 figure is really too much..