I don't think Blackwall will be an LI cause well Sheryl Chee described him as her Father....why would she be writing an LI that makes her think of her Father?
I think what she said was that Mary Kirby kept telling her to stop making Blackwall like her (Mary's) dad, wasn't it? I thought that was the tweet, unless it was something else. It's not a great sign for him, though, yeah.
Back on the topic of romances, I think it's likely that Solas may be a gated bi LI if Vivienne is in, but I don't think it'll be dwarves like some people have guessed. This is the issue with IB that I mentioned. David Gaider has been very clear in multiple places that they are determined to give everyone two options. In the panel, they said they used the chart to make sure everyone would have options, even by race. (The example they used was, "we can't do this, it would totally screw gay male dwarves".) Since IB was planned gated and we can be pretty sure it was against at least dwarves due to rigging, I think we can assume the remaining male wouldn't be gated against dwarves. They needed someone to fill that slot if IB went through gated, as planned. I would assume his gates are likely Qunari in this case.
However, if Vivienne is not a romance, I think Solas will be an ungated bisexual male option and Varric will be a straight gated option with Cullen having the gate(s) as the second gated LI and sort of attempting to make up for the extra straight option. This scenario actually makes a lot of sense for all characters involved, although I do not like the imbalance it creates.