Hi Anne-Laure,
I don’t know of any plans. I will add that the Instant class is documented to use a strange time scale, UTC-SLS, which changes the duration of a second near leap seconds. Whether anyone uses it in the manner documented is an open question. The Java Clock interface does not specify any accuracy requirements (so implementations can just ignore leap seconds to be accurate to 1 s) and conversion from other time sources to UTC-SLS is up to the user.
https://docs.oracle.com/javase/8/docs/api/java/time/Instant.html
Regards,
Evan