40%*
http://coh2chart.com/
axis are 60% in 4v4, USF/Sov are 63%, and UKF is at 70
Looking back, axis were consistently in the high 80% winrate (many times, in the 90% range) as far back as the chart allows (July 1st). Allies were lucky to be around 50%, until UKF were added to the game.
Common sense and personal experience is telling me that A) UKF was a new faction and everyone wanted to play it, coupled with B) US and Soviet were being propped up in 4v4 by the UKF.
Now that the new faction smell is wearing off, and things like the crippling brace nerf, the needed bofors and partisan nerf and vickers bug fix is in place, I think we'll see axis return to 4v4 dominance, and the leiG is going to be a major unit to carry them there