I think people will not lose interest even if Bitcoin die but interest is the feeling of wanting to know or learn about something or someone,on this point, learning has no end. It is possible to loss interest on something and later rebuild interest on thesame thing. Finally,Interest lost on Bitcoin could affect the entire interest on cryptocurrency technology.
I don't think this is the right way looking at this matter. The interest is all about the bitcoin and OP is asking what would happen if bitcoin dies. Will it really drive people away from bitcoin and will they be attached towards the alt coins etc.
According to me I really believe that people will have to put their money somewhere so they will choose some of the best coins in the alt list and then they will transfer the funds in there. Because bitcoin would be a lot for the fiat conversion and the fiat conversion might shut temporary so people will have no choice but to invest into alts. This is what might happen according to me. It could be forceful transfer or may be individual.