After three No. 1 weeks at the weekend domestic box office, “The Help” looks like it may have to cede the throne to Warner Bros.’ “Contagion.”While estimates are very early, B.O. observers are putting the Steven Soderbergh disease thriller’s weekend take somewhere in the $18 to $20 million range. “The Help” was expected to drop by about half from last week, putting it somewhere close to $10 million. “Warrior” doesn’t look to be tracking much differently from yesterday, and early numbers suggest the Lionsgate sports pic will pull in somewhere between $7 and $8 million this frame. Observers are putting “Bucky Larson” under $4 million, but it’s early — the Adam Sandler-produced comedy could pop with nighttime auds.