It is obvious that if they can consider releasing him as a political pawn that he is being held for political purposes in the first place. If his release was a danger to US security it would be completely irrelevant as an incentive. It becomes clear that he is only being held at this point out of spite.
Saudi king to meet with Obama on Friday amid Gulf concerns over Iran deal (Reuters)
from the article: Pollard's actions 'exceeded only by Snowden,' ex-U.S. official says