They became irrelevant. There was no sedan version being built. The commodore became the main car, and I imagine the platform was too small and weak for a commercial version.
Holden had started selling the Isuzu commercials and what bean counter would ever agree to having a Commodore competing against a Kingswood, and a Isuzu competing against a home grown commercial vehicle.
The other main problem was tradies were becoming more aware that utes and vans were actually useless compared to a one tonner or a bongo van.

However you can take Ford as an example of what could have happened I suppose. Start with the XD in 79 and just keep taking the latest sheet metal onto the front for the rest of time lol. they widened the opal to make a commodore, so it stands to reason they could have widened the commodore from to fit the WB?

I would say they would have dropped the V8 in the follow on from WB. They had already dropped the 5 litre. They clearly though "economical" engines were the way of the future.

WB were popular because they had a more modern front, body mouldings and taillights. They looked more like a commodore than a 70's kings wood. Thats why they were the go in the 80's. Just the same as a VG/VP commodore ute is way un-cool today. They are out of date. But you can get some cred with a VS.