Reading the Opel and Holden press releases side by side, also gives a new perspective on weights. I don't know which is right, but both mention 'up to 200kg lighter' depending on trim - compared to the old Insignia, and I presume old Commodore. That's pretty sloppy in itself - but it also gives an interesting twist or spin on kerb weights. When I compared a VE SV6 in 2012 back to back (next week) to an Insignia diesel wagon, the Insignia was nearly 100kg heavier. Yes, that was the old motor, and 2012 model shell - the 2013 Insignia was lighter IIRC. But, it was also a lot smaller inside.
I suspect, this is like the Camaro Gen 6 specs, where up to 400lb was claimed is very selective. Yes, if you compared the base I4 to the old SS....... the actual body in white dropped 66lbs, most of which was probably due to it's smaller footprint. A 1SS Camaro is now 3685lb - down from 3860 in Gen V. The engine is 50lb heavier due to DI, compared to the LS3. The rest of the car has extensive lightening to boltons - which you could apply to the Gen V. Given the VF dropped, model-model around 100kg (not counting things like HUD in VF SS-V and Calais, which is 40kg alone), in theory a Gen V with VF-style changes to the structure and underpinnings could have been within 50-60lb, and it's a lot bigger car.
I would suspect most of the '200kg' in Holden's case is comparing base I4 '17 to something like an SV6 or Calais - maybe even a V8, they don't weight a lot more. The old '16 Sport-tourer with a 2.0 SIDI weighed 1685kg 'minimum' kerb weight. The Evoke Sportwagon scales in at 1717 - and as noted, it's a lot bigger than the old Insignia, and still bigger than the new one. So add AWD to the '17 and I'm tipping, given it's going to be the 'top trim' model it's going to scale within a passenger's weight of an existing VF wagon with a 3.6, and probably about par with the Evoke. Maybe a small boy's weight in it.