Most Instrument training will be done on EASA aircraft and an IMC Rating is not valid for these.
Could you please point me at any document that states that holders of JAA licence with an IMC rating included in it, is no longer valid! When the JAA licence is replaced, the IMC if valid will be replaced with an IR(R), but there are still a good many JAA (now deemed to be EASA licences) that contain IMC ratings and indeed are being used in EASA aircraft.