Apologies for a Victorian jumping into the convo....
It seems the original plan for the 3000s was to electrify them.https://en.wikipedia.org/wiki/3000_class_railcar
That was 2008/9.
With the orders of the 4000s from Vic, I can't see any reason why Adelaide wouldn't continue in that fashion. Ordering more as more lines get lecky. Especially as the electrification is set to be staged, and seems to be severely delayed in it's rollout presently.
Thus, slowly scrapping the 3000s.
The only hiccup I can see in this, is if Bombardier is unable to meet the requested delivery capacity because of other existing build commitments (see below).
With regards to using these in Victoria, I see this as extremely unlikely. We already have Sprinters for intercity services. And have had significant orders for Vlocity trains for regional lines from Bombardier.
From what I can see the Vlocitys may eventually replace the Sprinters in Vic at some future point, depending on specific demand. But they are only a reasonably young train. https://en.wikipedia.org/wiki/V/Line_Sprinter
There would be a case to use the 3000 for inter-regional travel. Say Bairnsdale to Warragul on the Gippsland line. But the sprinters could be used for this too should such a business case ever be presented.
From what we now know, the Vic state government wants to unify it's rolling stock. They have just indicated that they intend to build 'long haul' Vlocitys. These will run alongside the N Class loco and carriages for the seeable future. So at some stage, Loco hauled passenger trains in Vic may come to an end. But that's too far in the future to say for certain.http://www.premier.vic.gov.au/labor-governments-regional-rail-revival-continues/
So I don't see it as likely for the Vic government to purchase any 3000s, especially given their age. They unlikely share much underpinnings with their Vic Comeng electric counterparts anyway.
The only way I see this happening, if the inter-regional runs get the go-ahead, and the Vic governments want to use them as a temporary solutions while other Rail Motors are on order. Or if the use of Sprinters on same become stretched...