If we don’t upgrade the Hubble now we’re supposed to have an even better next generation space telescope available in what, 0.0000001% of the lifetime of the Universe. I don’t think it will change much in that time. The only harm will be to the careers of a few astronomers who will have less data to analyze. If we don’t get the space station finished, or at least the parts that require the Shuttle to be finished done, before the Shuttle’s croak, then we’ll risk losing the space station. That’s a more important and more expensive loss.
Here's a question for ya: What is the space station for?
I will venture to suggest the answer is: "to be there."
Nothing else.
Do not take this to mean that I'm against space exploration. If I were, then I wouldn't mind letting gubmint suck all the oxygen out of it like they do.