The 4000s are refurbed 3000s...
Ignoring any factitious undertones, 4000's were unofficially listed on stabling diagrams, etc... to differentiate between refurb and non refurb 3000's. All 3000's are now done obviously so no need for differentiation.
4000's are the EMUs and thats that.
Also I love the assumptions made here about how things will work. How does anyone know there wont be a revamped Gawler line timetable to run EMU's from Adelaide to Dry Creek? Rumours have it they will purely because a) they can and b) they have the railcars to do it.
It obviously is so they can get the EMU's to Dry Creek for servicing, but this does not preclude operations on that section in revenue service.
As for 3000/3100 class, there are enough to operate Belair, OH, Grange and Gawler Central. When all the overheads are completed and Adelaide-Dry Creek is electrified, that will be the end of the Jumbos. All platforms at ARS will be electrified as part of this project. Work will start this year.