People talk. Unless a dev confirms anything I wouldn't bet on it. Doomed? You'll only be doomed if you've convinced yourself that you can only be happy if Cassandra is an option for you. Looks are important, but maybe you could consider that we know very little about their personality. I'm not suggesting you should stop hoping for Cassandra. I merely suggest you don't exclude all the other possible options if you don't want to end up feeling dooming.
Oh, we know more about Cass than we know about Viv or anyone else. Cass already had her own anime and we saw her in DA2. I think i already have a glimpse on how she is and those characteristics made me love her. Plus, we never had a lady romance like Cass, usually these romances end up dudes only. Which is annoying.
Who says Leliana won't be available? They've said before that doing romance arcs for previously romanceable characters was unlikely, not that it would absolutely never happen.
Indeed but they already said she won't be a romance.