You reminded of a sort-of related quote: When an expert says something is possible, they're almost certainly right and when an expert says something is impossible, they're almost certainly wrong.
I believe the quote is from sci-fi master Arthur C. Clarke:
When a distinguished but elderly scientist states that something is possible, he is almost certainly right. When he states that something is impossible, he is very probably wrong.
Any scientist's understanding of what is possible and what is impossible relies on currently understood theory. It happens rarely, but our understanding of what is possible at even the most basic level is sometimes upended (such as the discovery of nuclear forces, quantum mechanics, and relativity). The most prescient of scientists come clean on this fact when making predictions.
"It seems, therefore, on the whole most probable that the sun has not illuminated the earth for 100,000,000 years, and almost certain that he has not done so for 500,000,000 years. As for the future, we may say, with equal certainty, that inhabitants of the earth can not continue to enjoy the light and heat essential to their life for many million years longer unless sources now unknown to us are prepared in the great storehouse of creation."
Physicists can set the upper boundaries on engineering problems, engineers can do as much as they can to approach that boundary but will not cross it unless the first person was wrong.
Physics also identifies the dynamics, which are a special type of constraint. Engineers also consider economics, which usually limits you to far less than physics allows.
Still, it's true. Theoretical constraints that exist now might well be removed with new scientific insights. Trying to predict whether something is possible at all is useless given our limited understanding of things.
If an expert says something is possible.. it probably will be developed soon. If an expect says something is not possible, it probably will be developed (far) further in the future.
