UEFA president Michel Platini had called for the tournament in 2018, to be expanded to include more Asian and African nations.
Platini's suggestion came after FIFA president Sepp Blatter expressed his desire to reduce the number of European countries at the competition.
But Valcke does not believe that these proposals will come to fruition.
"Such discussions should be conducted at the level of the executive committee," he said.
"Never say never, but it's unlikely."
The 2018 tournament is due to be held in Russia, whose sports minister Vitaly Mutko denounced Platini's proposals as "disrespectful".
"FIFA will take the final decision, but it's unrealistic to change the demands when we've already got to the stage of discussing the calendar," Mutko commented.
"Of course, everything’s possible, but you need to respect the country that's carrying out the preparations for the tournament. We're preparing on the basis that 32 teams will be taking part."
