Governments generally honor old currency to maintain economic stability and trust. They would be shooting themselves in the foot. 

Declaring large amounts of existing currency invalid overnight would cause chaos, legal challenges, and undermine confidence in the banking system. 

When Iraq revalues, the central bank is more likely to phase out old notes gradually or allow exchanges, not outright invalidate them. Which is written in policy. 

There is no written policy in Iraq that supports any theory that shares this thought pattern among those who agree with this subjective thinking. 

For instance, in 2003, the Coalition Provisional Authority introduced new dinar notes to replace those bearing Saddam Hussein's image. Both old and new notes coexisted as legal tender during the transition, allowing citizens ample time to exchange their old currency without sudden invalidation.