Over the weekend the BBC played an ultra short teaser clip for season 13.

There's nothing new to see in it but this is likely the BBC warming up for release.

Already confirmed for a UK 2021 release there's not much time left anyway but we're still without a date.

There has been no official word for Australia but we would expect a near simultaneous release here.

References

Wikipedia. Doctor Who (series 13). (viewed October 4, 2021) 

Who Space [@DrWhoSpace] (October 3, 2021). SERIES 13 TEASER. Twitter.