At some point in the future, it will probably become the common view among Real Serious People that human-level AGI may actually be imminent. That might happen because AI reaches some technological threshold such that it becomes obvious that AGI might be coming soon. But I think it's more likely that the change in common view will be because the Overton window will have shifted, and it will suddenly become socially acceptable among Real Serious People to express the view (to others and to themselves) that AGI might be imminent. The Overton window shift may itself be caused by AI reaching a particular technological threshold, but I don't think it's the same technological threshold that would be needed if the cause of the viewpoint shift was due purely to the available evidence. (It's also possible that we'll get to human-level AGI even before the Overton window shifts enough to accept that as a reasonable possibility.)
An Overton window shift might also be due to factors that aren't tied so directly to AI reaching a particular technological threshold. Maybe some particularly well written book comes out, or maybe a sufficient number of well-known Real Serious People publicly state that they think AGI might be coming soon, to the point where it becomes socially acceptable for any Real Serious Person to think that as well. Or maybe it's just an accumulation of Real Serious People telling each other privately that I know this sounds crazy, but off the record I think it's maybe possible that AGI could be sort of soon, what do you think? And at some point that becomes more and more in the open, until suddenly Real Serious People notice that it's socially acceptable to think that now, so they do.
The point of all this is that we might see a sudden shift in viewpoint among Real Serious People towards thinking that AGI is imminent, but the cause of that shift might be at least as much a social thing as it is a response to some new evidence.