Almost immediately following this announcement, the value of the naira started falling, about 3.5% within two days. People are moving their expiring bank notes into dollars. But since the foreign currency dealers (also known as bureaus de change / BDCs) are not permitted to obtain dollars or other foreign currency from the banking networks, this new demand for dollars will likely push the "parallel market" rate (the "free market" rate) even higher.
However, following the latest announcement, politicians have approached BDC operators to easily convert their soon-to-expire stockpiled naira to foreign currencies, as the apex bank gave all Nigerians six weeks to return all old naira notes to the bank’s vault.
Dollar hits N785 as politicians flood BDCs with expiring naira notes https://gazettengr.com/dollar-hits-n785-as-politicians-flood-bdcs-with-expiring-naira-notes
Some will move those funds into bitcoin, stablecoins and other cryptocurrencies as well.
Also see a related post, found here on SN, on the naira valuation drop: