I guess we will know by Monday.
That is the fun of the NFL; all 32 teams could make the playoffs and, while if the worst make it and it will be a surprise, it still reasonably possible and week one all the world is fresh and new.
Dallas knows their D was a huge problem last year. They have absolutely been working on it. Their offense is absolutely top shelf. And San Fran's D is decimated and that is of late, not something they could plan for and I think their O really isn't all that good. That O line makes up for a lot of questions elsewhere.
I think Dallas wins this one going away.