The old bathing pool site has been proposed for development since before it was demolished in 1993 and it was designated for housing, in spite of complications with the site, in particular the presence of Southern Water storage sites on the eastern end of the foot print of the actual pool and further service pipes running east from those tanks.
The tanks have to be accessible at all times and the car park to the east of the tanks will need to be available for for this purpose.
The council previously designated the site for housing, in spite of also proposing that it should be restored as a destination site, as part of regenerating the local economy. In the new draft plan
In the draft plan it is now designated as mixed use for residential, commercial and leisure, but still with a target of 120 houses, which seems and an improbably high number.
There was an exhibition about the Old Bathing Pool Site on January 25 2025 and out of that Anna Sabin has put together a plan, incorporating the many ideas for the site into a possible layout:

The light brown areas are for housing
The dark brown areas are existing housing and other buildings
The yellow and green blocks cover the eastern part of the old bathing pool itself
The dark blue area is the part reserved for Southern Water and parking

The current situation is still unclear, but it is certain that on 10 June 2024 Hastings Borough Council signed a lease for 250 years from the 9th June 2024 until the 9th June 2274 with West Marina St Leonards Limited and pursuant to an agreement between the parties to the lease and Generator Group Ltd of 8 October 2021 as varied by a deed of variation date 1 August 2023, between the same parties.

An incomplete copy of the lease has been filed at the Land Registry, it is missing pages 14, 17 and 18.
The missing pages appear to cover how the lease is to operate, but there are break clauses after 5 and 6 years if planning permission has not been submitted or has been refused: the relevant clause 30 is not complete since it continues on to the missing page 17.

It is believed that if houses are built on the site, then the Council with the developer will sell the new houses with the freehold and that flats will be sold as commonhold. “Commonhold is a form of ownership (or tenure) for multi-occupancy developments. Each unit-holder owns the freehold of their home, and a commonhold or residents’ association owns and manages the common parts of the property.” (reference the Law Society, click to access)
The Generator Group presented proposed plans at an exhibition in 2025 which was reported on in the Hastings on Line Times, click to find the report
https://hastingsonlinetimes.co.uk/hot-topics/home-ground/developer-unveils-proposals-for-old-bathing-pool-site