Once it was rejected, Roddenberry considered shooting more material to expand it into a theatrical film, but ended up cutting up the color master of the pilot to turn it into the "Menagerie" 2-parter, which is why the only "intact" version of the pilot that survived was Roddenberry's B&W print.
An interesting "What If?" here! What if The Cage
had been released as a movie in theaters and become successful? Would Roddenberry have just gone on to do more movies, or would he have continued to pursue Star Trek
as a TV series? what would a series of Star Trek
movies in the mid to late 60s have looked like?