I don't think dollar would come to an end for another 50 years at least. Bitcoin is not that popular to take over.
Right now Bitcoin is not that popular but the Dollar will crash it should become more popular. The Dollar may not end soon but it will lose most its value as the number of Dollar in circulation increases and it becomes a smaller portion of exchanges and reserves in the world
I think that the dollar never coming to an end, because it is not only money, but also a world currency (international means of payment).
There's a lot of fud coming from both pro and anti-USD, but the dollar isn't invincible and constantly printing more and more can certainly be disastrous. Only time will tell what truly happens but people have been announcing it's collapse probably since it started.