The estimates might well be genuine at the time of publication, but our response to them will make the estimates inaccurate. Maybe all we're managing is to maintain equilibrium rather than positive progress.
I don't assume intentional dishonesty here because the risk of being completely discredited is way too high.
We're talking about the prediction "These glaciers will be gone by 2020".
And I'm not going to subject myself to a bunch of science denier sites to come back with a list of other failed predictions, but there are quite a few of them. Ones that are far more dire and breathless than a tourist trap going away.
If there's a risk of being discredited, it doesn't appear to apply to this topic. Intentional dishonesty? Nah, this is more like depraved indifference. There are no consequences for speaking out one's ass, and most attempts to enforce those consequences socially gets one branded as a "denier".
If the science doesn't support a deadline, then you don't pull one out of thin air while passing it off as a scientific conclusion. To do otherwise is dishonest, even if you think you're doing it for noble ends.