As long as I have been alive, these fixtures are mainstream in commercial lighting. The original ones I think have 4 f40t12 lamps and 2 magnetic rapid start ballasts and has a plastic diffuser with one ballast controlling the outer tubes and another controlling the inner tubes. I have seen these fixtures in 1980s movies and TV shows, but how long have they been around?

Troffers have been around pretty much since the beginning of fluorescent, but I think the most common style seen today came out in the 1960s or 1970s.

Yup, early troffers were listed in catalogues as early as the 1940s, typically looking like modern 1x4 troffers but with deeper housings and glass instead of plastic. In some cases they were open or had louvers.
Rest-Glow
Curtis Lighting
Day-Brite 1941
Day-Brite 1947

At the time, most installations using troffers arranged them in long continuous rows and were 1-2 lamps per cross section although a few 4 lamp models were available. Fluorescent luminaires was still a mix between recessed troffers and surface mounted types such as half pipers and louvered fixtures. Various models were made, including ones for long extinct lamp types such as F90T17. These of course were predominately preheat, rapid start would not be introduced until the 1950s. Most building ceilings at the time were typically wire lath and plaster or 1x1 tiled so in most cases troffers were a lot harder to install compared to surface mounted luminaires.   

Modern T-bar ceilings were only patented in 1958 before then tiled ceilings were typically attached using furring strips with screws, adhered on, or was a removable system where the tiles needed to be removed sequentially. The 2x4 troffers designed to fit into a T bar ceiling probably came out in the late 50s as well. By 1960 troffers resembling modern 2x4 troffers were in catalogues.