The biggest stat for a QB is W or loss. I think if Josh improves on decision making, gets a bit more time, and has more weapons- he will get more W’s. I’ve seen him with significantly improved stats if you figure in drops. I’ve also seen stats that have him as a bottom 5 QB based on some unique set of stats.
If the above happen he will get the W’s and stats will improve somewhat. But given he plays in WNY and has away games outside his clean weather games ( particularly wind) are much less than say Brees or Ryan. So he will likely never be a top 5 stats QB. But gives his leadership, arm talent, and now weapons around him he can be a top 10 QB for several years. With a ceiling that might be as high as anyone. As many have said with the Bills core and some improvement JA can lead this team deep into the playoffs.