I think if an altcoin is going to rival bitcoin it will need to do something unique, have a specific purpose and not just be a copycat of bitcoin.
ETH as an example is doing just that, I do think at some point we will see a newcomer that will outshine bitcoin but when is the question.
It's almost a year after. Do you think any altcoin currently has what you describe as "having a specific purpose" asides ETH that you already mentioned? I want to say EOS because it seems to be an improvement on ETH but I would like to know your thoughts.