Back in April, there was speculation that Nokia was debating whether or not to include a dual-core or quad-core Qualcomm Snapdragon 800 in the Nokia EOS handset. For a Windows Phone model to be compatible with a quad-core processor, it needs to run on the GDR 3 updated version of Microsoft's mobile OS.
At the time, we said that Nokia was looking at battery life to determine whether or not to go ahead with placing a quad-core processor inside the photo-centric model. There is talk that Nokia is having problems with the battery life on the quad-core models it is testing which probably means that we will see dual-core silicon on the Nokia EOS. But the benchmark testing indicates that there will be a quad-core powered Lumia model eventually, possibly by the time that the first Nokia Lumia phablet is released in the third or fourth quarter.
source: GFXBench, Androwin via WMPoweruser