Not V8’s that’s for sure!
Better to wait for the ZC (if there ever is one and/or Holden haven’t gone tits up by then). Never a good idea to get the first in a series.
The way this is going there won't be a ZC.
Opel have been sold, and while the first (rubbish) Insignia was in production for about ten years, this one was only ever intended to run for 4-5 years before they switch over to an all-Peugeot/Citroen base model. (the Grandland is actually a Peugeot 3008 for example) Most Euro cars have gone that way. The Renault's are all basically Nissan's with not much more than software and different body panels (even that new Mercedes 'ute' is a Nissan). The little Chryslers are all going/gone Fiat under the skin... In Europe there is a courier van that is sold under about 5 brands (Opel Movano, Vauxhall Movano, Nissan NV400, Renault Master and I believe it is also rebadged as a VW or Merc). In each case the changes are so minor and cosmetic that if a line of them were in front of you, you could blink and not notice.
It seems that the next commodore (if one comes) will either be something from somewhere else in the GM stable (an up-sized Chevy Impala perhaps? or maybe a Buick LaCrosse? or maybe even a caddy 4-door?)... or it will become one of these crossover AWD wagon things like what Opel/Vauxhall do to the Astra to create the Zafira in Europe?
Edit: I just read (well... poorly translated from German) that the base for the LaCrosse and Malibu are both Insignia as well. It is expected that the next version for the Insignia is anticipated to be similar to the current Peugeot 508 - which (in SWB version) is the same as the Peugeot 3008/GM Grandland. So maybe GM/Holden are going to just continue this badge-engineered folly. Damn