Technologies fade away when they are no longer useful, cost/benefit ratio is too high or something better comes along.
It is question of when.
The technology of warfare evolved to better mechanisms, perhaps same with computing.
We might design organic brain extensions, so people just become smarter, making LLMs obsolete. (Brain-Bluetooth interface for additional cost)
What we currently have is a simulacrum of thought - albeit a good one.
Any technology is useful only in the sense that it helps us with solving the problems we are dealing with in that time. When we face issues that a pseudo-thought is not useful in tackling or worse is one of the causes - this will recede in the background.
Beyond that, the implicit assumption in the question is that thinking is the highest form of activity that is useful to us.
I don't know how my thoughts arise but thinking happens when I engage with them. I think what we look for is meaning in our lives and thinking helps us generate/achieve one, whether real or illusory.
Castles still exist as well, you just aren't invited to them (which was true for us peasants back in the day, too). Trump is still trying to get one built under the ruins of the East Wing, in fact.