My guess is no one will look back and say "Huh, he was right".

The only thing that probably is going to happen is "Huh, why isn't that delivered?" and then they will look everywhere but on the fact that it was, at least partially, just a stupid idea in the first place.

Of course I don't know the exact situation so it's more of a thought on what happens in general in the industry.

At the risk of a totally uncalled-for derail into politics - this is a hilariously apt description of Brexit. It makes me want to reanalyze the entire situation from a project-management perspective. It suggests a possibly illuminating metaphor: party leaders = management + sales, the electorate = the customer, and representatives = developers and engineers.

That's naive.

Nobody will revisit the GP's reputation, and after the novice devs fail to do the work people will just scatter into different projects. They may or may not take a reputation hit, while the PM that insists so much on doing the not viable work will take none of it.