It couldn't be that hard to add two seats a car, right? Things can change between now and the 2018 opening day, so we've got a while to see if anything changes.
Trust me, the basic design concept won't change. No chance at all. Whatsoever. That would require SFFT and RMC both to scrap several months' worth of design work, and basically start from scratch again - in which case you wouldn't see this coaster open until 2020 or so, maybe 2019 at the earliest, it would look nothing like the unveiled design, and all in all be tremendously expensive for everybody.
I'm afraid that the "public unveiling" milestone we enthusiasts see as the beginning of the project, actually is close to its end for those involved with it. At that point, the specifications are nailed down, the design is finalized, contracts signed, prices negotiated, payments secured, orders placed, construction scheduled, everything is done and dusted, all that remains is to build the thing. The production phase is the earliest phase visible to the public, but for many contractors it signals the end of their involvement. If SFFT had wanted double-width cars on this, it would have had to be changed in the pre-design phase (last year or so), or possibly in the design phase (but that would already approach the deadline where making significant changes would be prohibitively expensive).
Since this coaster involves an external IP, I think even changing its colour would be too expensive at this point. It would require a new round of meetings with the IP owners and new stamps of approval that the rest of the process can't afford to wait for.
But hey, as somebody said above, it won't be
that much worse capacity than a standard S&S Free Fly. I think the park has calculated that it will be fine for them, since there's no way they haven't considered that aspect thoroughly already.