Sad day for radio, but 2CH isn’t entirely dead, technically 2CH is only a format change, yes 2CH isn’t going to be used on air & it’s not a Classic Hits or Oldies music station any longer, but the licence holder is still Radio 2CH Pty. Ltd. & the official ACMA Callsign for 1170 is still 2CH.
If at some time in the future SEN wake up & realise they made a mistake & SEN sport on 1170 in Sydney just doesn’t pay the bills, there’s nothing stopping a new buyer changing back to a music format & IDing as 2CH once more.
4KQ may be a different situation though, currently ARN is the licencee, so the owner will become SEN, & we’re yet to see if the 4KQ callsign stays or SEN change it?