Definitely not a lost cause. I went from having my dogs being allowed on my bed to one night deciding I didn't want them to be anymore, and all it took was telling them to get off if they tried and not inviting them up anymore. They got the hint, and honestly after night two, they never tried again.
I think furniture could be the same. Dance was always allowed on furniture for the first three years of her life, then we moved and the furniture we had was too sensitive for dogs, so she wasn't allowed anymore. She was a bit confused, but understood pretty quickly that the furniture was suddenly off limits.
Dogs are pretty adaptable. I think there is nothing wrong with new rules at all, as long as you're consistent with those rules.