I wouldn't say it's immortal but it will be the most long lived. Some new better unimagined technology may come along some day, quantum money that doesn't even need a ledger for instance......don't ask my what or how, the point it something better always comes along eventually otherwise we'd still be trading with shells and stones.
I don't see any other cryptocurrency replacing Bitcoin though, they have their own use cases and roads to walk.
BTC doesn't need to be something that would bring results in a day or so and break through with technology and hype - it should just stay on its course and adapt if needed, that would put it in the best position possible.