Every thing I’m about to say is what I understand it to be so it could be wholly inaccurate, slightly inaccurate, correct or a mixture of all!
The Maidstone depot, as I understand it, will be at Chart Leacon (when it is finished!) and is/will be a SE depot.
The Thameslink services (currently at Ashford depot doing Sev to Bfr only) from Maidstone East to Cambridge (which have been mothballed again!) will need to be run from here, otherwise it would appear that the service cannot get started.
I’ve heard that SE are not playing ball over ‘sharing’ so who knows what will happen.
Taking into account the government ‘taking over’ the tocs, anything can and probably will happen in the future.