Reza Shah officially changed the name BACK to Iran, cuz that’s what it was in ancient times.
The name “Iran” is Persian for “land of the Aryans” and has been used internally by the Persians for centuries, much like we call ourselves ‘Americans’.
But, as with “America”, which refers to the USA and any nation in the entire Western Hemisphere, ‘Iran’ is has always been a generalized term that refers to a people and a vast region - not just Persia.
Iran was never the official name of Persia until 1935, and until 1979, the name Persia was still widely used and accepted and remained on maps and other official documents.
I don’t know how old you are, but I was 25 when Persia became Iran - and despite the Shah ‘officially” changing the name in 1935, we all know it was 1979 when Persia became Iran - and we all know what happened in 1979.
So don’t be so sure the Persians won’t prefer to revert back to ‘Persia’ if the Iranian regime is toppled.