Do you think a real life Biography of Behind the set of Threes Company actors will ever be made into a motion picture ?

You're 10 years late. It happened in 2003 already.

Well, maybe not in theathers, but it has already been done for TV. See http://en.wikipedia.org/wiki/Behind_the_Camera:_The_Unauthorized_Story_of_Three%27s_Company

I think a Three's Company film could somehow work for theaters, i am sure people who are big fans would pay to see this film, only if they can find actors who look exacly like the characters on the show