That future isn't inevitable but highly likely given on the trajectory we're on. But you can't specify a timeline with certainty for what amounts to some highly tricky and very much open research questions related to this that lots of people are working on. But predicting that they are going to come up completely empty handed seems even more foolish. They'll figure out something. And it might surprise us. LLMs certainly did.
It's not inevitable that they'll come up with something of course. But at this point they'd have to be fundamentally wrong about quite a few things. And even if they are, there's no guarantee that they wouldn't just figure that out and address that. They'll come up with something. But it probably won't be just faster horses.