"Continuance" is of course what we all want and hope for.
There is however a realistic chance that that may not happen, in which case we have to fall back on "grandfathering". In that case there would be a cut off date. As Slopey says if the CAA are issuing IMCRs on JAR licences until 30th June then one would hope that any cut off date would not be before that, but who knows?