Someone has to find the time to do a commit review on the patch.  As Guilherme said, there's no specific maintainer for wave, so I'm afraid it just got forgotten about.  On the other hand, as a new feature it would now go in 3.5, and we're at the start of the approximately one year window for new features, so if you ping this issue (as you just did) periodically, someone will get to it ;)

What you could do to help move it along is to do your own review of the patch, including making sure it still applies to default...which it may not, since there have in fact been some changes in wave.py.  If that's the case you can also help by updating the patch.