Any plans were interrupted by the Turkish war of Independence, but what were allied plans? To give it back to the Ottomans? To hold it permanently? To give it to Greece?
There were plans and agreements about Istanbul between Russia, France, and Britain which is interrupted by Bolsheviks’ revelation in 1917, before the Turkish War of Independence.
Tsarist Russia claimed the city and promised Ottomans' middle east lands to France and Britain.
But nothing went as expected after the date of these secret meetings and agreements. Britain forces couldn't pass the Gallipoli at ease. Tsarist Russia couldn't prevent Bolsheviks take over and they pledged to withdraw from the war. France had a change of priorities against Bolshevik expansionism.
Britain occupied the city in 1919 but they had to withdraw 4 years later as a result of Turkish victory in Anatolia and the political pressure in their country.