The current status is that VoLTE is available in beta form for the Xperia 10 III, and we’ve also said that we aim to to roll out support for the Xperia 10 II after further testing is complete. We’ve not made any commitments one way or the other in relation to other devices.
As you point out, the Xmas 2021 “Buy one get one free” vouchers are valid until 30 June 2022, and there’s not currently any plan for that to change.