you are asking two different question:
the probability of bitcoin being replaces in the future is high.
BUT
the probability of bitcoin being replaces by ethereum in the future is zero.
ethereum is just another one of those pump and dump altcoins with a lot of hot air a lot of shills to advertise for it. but over time it is going to die off and disappear just like others before it.
Well, don't underestimate the success of scammy systems. Look at the three highest alt coins: ETH and DASH, both heavily centralized, both having serious historical problems (one has lost its immutability and permissionlessness, the other one a huge instamine). The third one a banking coin with full premine.
The two more "honest" coins are Monero and Litecoin at the top of the palmares, with much smaller market caps.
There's no guarantee that crypto markets value decentralisation or permissionlessness. It seems rather the opposite. They may just as well prefer scammy games. Bitcoin being centralized by miners, ETH being a totally centralized coin having already shown what that means, DASH being an instamine centralized coin, and ripple being a bankers coin, take up 95% of the crypto "investment".
In a way, this is not surprising: centralized systems can manipulate much more, and market much more, than decentralized systems which are no game.