I'm pretty sure that the neighbors whose subwoofer has been a regular irritant for the past year are in the process of moving out. I should know for certain this weekend, but everything I've observed indicates that they're on the way out by the end of the month. Yes, they did turn down the bass somewhat after I said something last fall, but even at this reduced level it was still something that would come pulsing through the one shared wall. It just didn't rumble through every room in my place after I spoke to one of them through a narrowly cracked door.
There's the risk that whoever replaces them in that apartment will be worse, so my relief at their departure is tempered by the uncertainty of the unknown. Regardless, it's out of my control. Such is the way of apartment living.
For now, though, I will enjoy the peace and quiet as long as it lasts and hope for the best.