Printing is just not very expensive, relative to the size of the US economy. People like the $1 note. I just don't think it's going to happen for another 2x-4x reduction in the value of the note.

Give it 15-40 years and we'll think about it again!

Of course, by then, so much of commerce will be electronic that I don't think anyone will care about what notes still circulate, other than the $100, which is used more outside the US than inside.