The NSA is only going to spend so much time trying to crack my specific password on 100 billion dollars of hardware. If I have a 6 word password (barely harder than XKCD) (72 bits), .1 second local hashing, and their computer is ten billion times faster than mine ($10 per my-computer-equivalent), in a month they'll get through 0.006% of the search space.

The "decades into the future" part is a much bigger threat than their ability to out-compute me in the short term.