Do you believe that they're based on any actual statistics and/or considering the coin's potential, are they purely fictional?
There seems to be no way of knowing how long a cryptocurrency will last in its early stages, or how long it will take to bounce back after a crash—we also don't want to predict these things to be relatively speculative. There are many different factors that could potentially contribute to any of the possible outcomes and even if one factor increased, the other might decrease in return. Moreover, all of these findings are highly context dependent, making them difficult to generalize universally.
If we are honest the only coin that we know is going to last until 2050 is bitcoin, no other coin comes to my mind when I think about such a long time frame, now there are a few other good coins out there like ethereum, but even ethereum is not a sure thing as a lot could happen during that time, so we must disregard those predictions as what they are, baseless speculations, and ignore them as there is no point in taking those predictions seriously.