To believe (e.g. to be certain) something like that does not make rational sense. To say that is a statistic probability makes much more sense. However, this has been discussed over and over again. In order for the cryptocurrency space to thrive, it would be most suitable if there were multiple coins at the top and not just one (as currently Bitcoin is). Nobody can say that either one will happen for sure; they would only be speculating.
I doubt that there is any other cryptocurrency or altcoin that can supersede the bitcoin. At least not for the next 5-10 years. Of course there are many rising competitors like ripple and litecoin. k down the road potentially, but as of now the focus seems to be on how to make Bitcoin better, safer and more accessible.