I've got the book here and a complete text dump of it and scanning the latter (searching for keywords) I am finding nothing to support the idea that a feature was in any way anticipated. So far all I can find is:
After Justman read the latest script rewrite, he began the schedule and budget “breakdown” process. Not only was the film equivalent in length to any movie,* it was replete with enormously difficult production challenges, special effects and optical effects that had never even been attempted on a television schedule and budget. Some of the optical effects would require time-consuming tie-in elements that would slow the filming process.
...and...
A year earlier, Jeffrey Hunter had rebuffed Roddenberry’s request to shoot added scenes to lengthen the pilot and attempt to get a theatrical release for it. There was no way Hunter would cooperate to redo it for a television episode.
*Debatable.