If this is a origin movie, I am not going to watch it. Why should I pay for something that I already know?
By that logic you probably shouldn't have seen the first Iron Man, Thor, Captain America, or Avengers films (since all were origin stories, in the case of the Avengers film it was an origin story about the team coming together).
Anyway, I believe they've already said it won't be an origin story. That may have changed since the director was hired (the script may have gone through some changes and added in an origin).
If they do an origin, it'll be a quick flashback type thing, most likely, instead of focusing the whole movie or first half or whatever covering the origin.
Besides, you need to remember that the general audience probably has no clue about Dr. Strange, and thus an origin story in the film would make sense for the larger audience outside of the hardcore comic fans like us.
Thus, if they do an origin, there's a logical reason behind it. If not, they'll likely cover his origin in a quick flashback or some dialogue.
But the chances are this will be a origin movie, as not so many people know about Dr. Strange.
At least make the different origin story...
You said it. I do think his origin will be touched on, just unsure how they'll approach it.
As for different origin story, it sounds like that may be the case with the recent casting of Tilda Swinton as the Ancient One, and Baron Mordo not being an outright villain but a sort of big brother/mentor role...?