From Sp15 onwards, #448866 going to phased out and it will be replaced by #549444. Technically to change from #448866 to #549444 should not have any impact in term of Heat Transfer/ Screen print – embellishment.
As for S/587609, as mentioned in my message dated Dec 23, “Resend with correct file attached. Fyi, im#444671 has expired. We are getting HO to reactivate. Will add back to bom once HO is back after the holiday”.