That's a very tidy looking estate car, and will deserve to go up in value as supply and demand dictates market price.
Very few are likely to go UP much in value, as the demand for Omegas is small. This has always been true of large Vauxhalls.
Smart, tidy, well-kept, usable examples probably reached their lowest value some time ago, and might recover slightly.
Snotters are, and have been for some time, worthless and won't get any better. These are not just the scruffy cars that have been ignored, but tidy ones that haven't had the more expensive jobs done because the car isn't worth much. We are the only buyers of such examples, won't pay much for them and even then will be very selective
Working estates are still properly useful cars, and will be in use for some time still. Owners know how hard they are to replace, so don't expect them to change hands. Which has been true of estates forever.
Very few car models break this cycle!