I think it has got something to do with the weather in Qatar during the summers. It wouldn't be kind on players to play on the heat that there will be. November will be much much better time and a weather that'd be friendly to all nations competing.
November is winter in most part of the world while in Gulf countries its a moderate weather where heat is bearable by all teams. I think its a nice move by fifa to organise the tournament in this November. While most of strong teams are from Europe, it will be a good test that how they play in such weather. Brazil and Argentina are only teams apart from European teams that can win this title.