I think it is not possible for some altcoin to overcome Bitcoin. All of the altcoins are Bitcoin based. I mean, look at the exchange sites, how can you buy an altcoin? Of course through Bitcoin (and some via Ethereum). Aside from that, Bitcoin is the one who started it all. Therefore, it is the mther of all coins. And lastly, it is the only coin with unknown developers. We inly know its developer by the name of Satoshi Nakamoto.