Understood.
I really hope you are able to get an appointment before the system changes but I think that it's highly likely that there is still going to be some sort of premium option available. It's pretty lucrative for them and I can't see them not continuing to take advantage of that.
Staffing costs are huge for any employer and this work has been contracted out to save the taxpayers some money. Services have to be self funding but immigration still isn't yet.
From the little I have read on this, it was something like 55 of the 60 centres will be post offices and these will be for the vulnerable eg refugees who can't speak English? That documents can be scanned to UKVI and in some cases, passports scanned too.
If any priority service is offered, I guess it could end up as it is now, where the more that apply for this the longer the queue gets? Unless they offer the £2,500 service for ILR, as Parliament was discussing making that cheaper if their application was easy to deal with and making that service a maximum of 2.5k.