Qualcomm recently announced the first quad-core chipset with Windows Phone 8 support (http://www.gsmarena.com/qualcomm_outs_quadcore_snapdragon_400_with_lte-news-6155.php) and Nokia may already have a phone with it in the works according to GFXBench results. The promised GDR3 update (http://blog.gsmarena.com/microsoft-to-issue-gdr3-windows-phone-8-update-by-the-end-of-the-year-support-for-1080p-displays-in-tow/) should bring quad-core and 1080p screen support.
However, the Nokia device that ran the benchmark had screen resolution of 720p, suggesting this might be a separate update.
The GPU of the chipset was Adreno 305, but unfortunately GFXBench didn