they certainly will.
i and no doubt many older members on here will remember cars from the sixties and seventies which normally lasted between 10 to 15 years absolute maximum until, the rust got them.door skins flapping loose,front and rear valance made entirely of filler ,the majority of cars over 5 years old had a yearly rising underseal layer all around the car !.
ive worked and restored many a car from this era and to be honest its a pleasant change to have something newer like an omega which doesnt realy rust compared to the older stuff.
yes sills will rust,wheelarches,etc etc but nothing even remotely like the older stuff and nothing that will ever render them scrap except in the most severe of cases.
modern cars die of electrical issues nowadays ( or garages that dont want to work on them so quote silly repair prices)rendering them "uneconomical to repair" to an average owner.
omegas will undoubtably remain in the hands of enthusiasts like some of us and will gain the same appreciation as any car would which was originally classed as an "everyday car".