Some interesting discussions about if the 560 will be "better" or not. Here's my take on it:
I think The HE-500 is the darkest of all Hifiman headphones (minus the HE-400 which is just darker in places). The HE-6/HE-5LE/HE-4 and even the original HE-5 was all lit up more. People describe their sound as airy, more detailed etc. The HE-500 is sort of a anomaly in the line, an accident perhaps. For me the tonality is perfect and is what I consider to be "neutral" from a subjective perspective. Even though I know the technical definition of neutral is probably a little bit brighter.
I have no doubt the 560 will be technically better. What I mean by "tech better" is that it will be more resolving of micro-details (a la HE-6) maybe have better soundstage (wider/deeper) and maybe even better imaging (more precise placement of instruments/voice etc). That's all great, same thing happened between the LCD-2 vs. LCD-3. What I'm afraid probably won't happen is that the HE-560 have the exact same tonality of the HE-500. What I mean by tonality = frequency response curve. I can accept something similar, but not something significantly brighter or darker.
There is a minimum amount of micro-detail extraction that is needed for me to enjoy my music. HE-500 provides this. It's not a HD800 or SR-009 but it has "enough" details and is transparent "enough".
I think Sennheiser drastically changing the tonality of the HD650 to the HD800 is the fear I have. If Sennheiser had kept the exact same tonality of the HD650 or even the HD600 but created a ring radiator driver with super micro-details and speed. I honestly wouldn't own anything else. I'd own the HD800 and nothing else would interest me.
So yes. I'm excited, but also fearful that Fang has gone super bright on us again.