Nobody really knows. BTC could be the king forever, or in 30 years there could be someone who takes its crown and crypto could be a whole diff. developed sector and everything with ETF's by then. Only time will tell but if there's a project w the same weight as what BTC has done for crypto and the world that could eventually grow to the strength of BTC, I believe it's this one https://bitcointalk.org/index.php?topic=3085831.0