Forrest said in an interview you see both those looks in the movie.
Correct. Forest Whitaker said to Entertainment Weekly’s Anthony Breznican that we’ll see Saw with both looks (shaved and with re-grown hair) at this link: http://www.ew.com/article/2016/08/11/ro ... aw-gerrera
And, Pablo Hidalgo reaffirmed Forest’s words at a SW panel in August that we’ll see Saw with both looks in the movie at the 32:40-32:52 mark in this video here: https://www.youtube.com/shared?ci=OxuQQWIDBv8
I mean I guess we can trust Pablo since he’s a story group man at Lucasfilm who’s worked closely with George Lucas like Dave Filoni has. So, maybe it’s a flashback or Saw loses his hair as he barely escapes from the explosion of the city on Jedha. Now, someone is probably gonna say they're just saying that because they're corporate people who want damage control. Well, if they were saying that, they wouldn't have a Funko pop bobble head of bald Saw out now at Walmart and a Hasbro action figure of Saw with hair coming next Jamuary. So, I trust that there will be a point in the story about what happens with Saw in the movie.