Probably in the new year.
A1 Steam Trust are already advertising 'Aberdonian' trips in 2023.
https://www.a1steam.com/a1-rail-tours/the-aberdonian
https://www.a1steam.com/a1-rail-tours/home
Railway Touring Company currently advertising to the end of March 2023
https://www.railwaytouring.net/uk-2023
Steam Dreams not yet advertising for 2023, but have indicated their intention to run the Windsor / Surrey Hills trips.
https://www.steamdreams.co.uk/steamexpresstrips.php
as well as the usual day trips
https://www.steamdreams.co.uk/tours.php
West Coast run the Jacobite, Dalesman and Scarborough Spa excursions.
https://westcoastrailways.co.uk/
Saphos Trains posted their 2022 schedule around the start of the year so would assume they might do likewise for 2023.
https://saphostrains.com/trips-tours/
Vintage Trains tend to publish their plans with a bit less lead time.
https://vintagetrains.co.uk/train-rides/
One of the big unknowns however surrounds the rolling stock availability with it unclear whether the existing rolling stock can work past March 2023, and it being left rather late to do anything about using anything else.
The obvious reason to take main line steam is to go faster than 25mph.