A couple of things. First, we've been in a declining long-term interest rate environment for a long time. This is a huge plus for the economy is a number of ways, large and small. Second, that time is probably over. It doesn't necessarily mean we're headed for a period like the mid-50s to the mid-70s, but there just isn't much room for rate to decline, even if they wanted to.
Third, rates are still at historic lows, and we've seen quick increases even during the last 20 years when the trend was down, so there's not necessarily reason to panic just yet.
Fourth, the middle part of that graph should remind us all just how quickly things can get out of control.