I didn’t realize this was coming up so fast, thank you Dennis Gilmore for announcing it today on -devel. Personally I can only think of one thing I want to make sure gets into 17 by GA that isn’t currently there, and that’s Lilypond 2.16.0. Since it should be out May 3, that shouldn’t be a problem. If anyone has anything they really need fixed/to fix before then that isn’t a blocker and an fix wouldn’t radically destabilize things, now is the time.
Ask for help on -devel if you need it. Tons of talented people read it every day, and so do I.