I think I'm with you on the fade away. But Opel won't be the long term supplier to Holden (while ever GM owns it).
After the sale to Peugeot/Shitgroan the Opel Insignia/Commodore and Astra are only going to be supplied on this model run which has a maximum life span of 5 years (maybe).
If GM still owns the badge/mark "Holden" after this contract expires GM isn't going to allow a French company to take their profits.

Who would buy Holden anyway? Australia and New Zealand is pretty much the only places who get that badge and Holden doesn't manufacture anymore.
Future Holden's will need to be GM/Chevrolet (even if re-badged "Holden") if the company is to survive at all. The writing is on the wall!