I would be extremely disappointed in Bioware if they turned down continuing the DA2 system, where everyone got equal options in the vanilla game, for one where one demographic got extra options. If the last two options were straight, I would not be pleased, no.
However, I strongly doubt this is the case. What Bioware has said is that everyone will get options and that equality between genders/sexualities is their first priority. Gaider said at a recent con that they used the chart to make sure everyone had at least 2 options, even by race. Everyone was always planned to have two options, but some may get more depending on the gates. With three originally planned race gated characters, and knowing Iron Bull was gated, we can be pretty sure that there needs to be another bisexual male, at least. See;
Dorian - available to every male
Cullen - available to every female
Iron Bull - not available to dwarves
This scenario meant that straight women and gay men wouldn't have 2 options for dwarves (for example, or whatever race(s) IB was meant to be gated from). IB was planned gated until very recently, so it doesn't make much sense that the others wouldn't have been planned around that. They said the chart was used to make sure everyone got 2 options. The example he used was even, "we can't do that, it would screw over gay male dwarves". By elimination of what they've said their process is, I think it's extremely unlikely that the last male is straight.
We know that Josephine is not gated and never seemed to be planned gated, so there still remains a chance that either Vivienne will be straight or she will not be an LI. However, since they've said their priority is with equality of gender/sexuality, I believe the options will end up as 2/4/2. I think Vivienne and one male out of the remaining will be available as bisexual options.