The same question i have in mind, but after learning people reviews i came to know that the value of bitcoin price is really high, after not mine able there will be a huge demand for bitcoin because of very low transaction fee. But now who are talking here may not live that many years how it is going to be in near future.
Until this happen, there is a long time yet, a lot of years and decades, more than one century! All we can say about it is speculation, it's too much time to predict something about, it's like when movies try to portray the future. I believe the BTC price (if consolided as main currency) will go up, and a lot. We could negociate few satoshis worthing the equivalent to $1 dollar or a bit more.
If the BTC will be successful, that is what will happen. But maybe, another crypto-currency can take the place of BTC and become more important. Only time will tell.