I'm pretty bearish on human interstellar travel or even long-term settlement within our solar system but I wouldn't be so pessimistic on unmanned probes. The technical hurdles seem likely to be surmountable given decades or centuries. Economic growth is likely to continue so relative cost will continue to drop.

Absent a general decline in the capacity of our civilization the main hurdle I see is that the cost is paid by people who will not live to see the results of it but I don't think that rules it out, I'd certainly contribute to something like that.

What are some of the other factors you are thinking of?