This will probably be enough time to reach a level of completion that will prevent wholesale cancellation. However, like Hubble, there is still the chance for severe delays post completion.
Note that The Hubble Space Telescope has cost on the order of $6 billion to date. I have yet to see anyone, even a crazy anti-science republican suggest that it was a waste of money. Even trying to retire the Hubble after a great mission lifetime resulted in a strong public reaction.