Long-standing fears over soaring temperatures in the country have prompted debate over the ideal date for the tournament, with Valcke confirming on Wednesday that a summer competition was impractical.
"The dates for the World Cup in Qatar will not be June-July," he told Radio France.
"To be honest, I think it will be held between November 15 and January 15 at the latest.
"If you play between November 15 and the end of December that's the time when the weather conditions are best, when you can play in temperatures equivalent to a warm spring season in Europe, averaging 25 degrees.
"That would be perfect for playing football."
However, a short while after Valcke's claims, Boyce and a statement from the governing body rubbished any suggestion that a decision had been made.
He told Sky Sports News: "I am totally and completely shocked. Absolutely 100% it has not been decided as far as the Executive Committee are concerned.
"It was agreed that all the stakeholders would meet, all the stakeholders would have an input and then a decision would be made. And that decision, as far as I understand, would not be taken until the end of 2014, or the March executive meeting in 2015, and that's the position as I understand it today.
"Whether Jerome was making a personal opinion or not I just don't know, but I can honestly confirm that this has not been discussed with the Executive Committee of Fifa."
A Fifa statement added: "The precise event date is still subject to an ongoing consultation process."