Joan Collins and Michael Nader had both decided to leave the show. Joan was willing to do guest appearances, though. So most likely, Dex would have been killed off and Alexis would have probably ended up in a coma or paralyzed and shipped off somewhere to recover.
Sable, pregnant with Dex's baby, would not have had a father for her child. Most likely Blake would have married her to give the baby a father. If Linda Evans were ever to return, the you-know-what would hit the fan!
Both Dominique and Jason were hinted at at the end of Season Nine. They were going to return in Season Ten. Dominique would have helped Blake against the Lauren Hutton character. Monica still had issues with Jason for disowning her and Miles, and Sable was hiding the identity of Monica and Miles' real father. There was talk that it was actually Cecil Colby who raped Sable.
I haven't read what was going to happen with Adam, Jeff, Monica, Fallon, Zorelli, Sammy Jo or Tanner. We can only assume there was going to be a romance between Jeff and Monica. Whatever happened between Fallon and Zorelli, and Sammy Jo and Tanner depended on whether the actors who played Tanner and Zorelli became contract players. Dynasty had a nasty habit of dropping characters after their Season Finales. I'm sure Adam would have stood trial for attempted murder, but who knows who they had planned for a new lady in his life. Sammy Jo or Monica would have been interesting, as they were the only young women besides Fallon on the show. Also interesting would have been an affair between Adam and Lauren Hutton, which would have been more likely!