Until the Retina version drops.
That could be a while. After all the iPad Mini has like 60% the battery of the iPad 2 and you are asking it to push out almost twice as much graphics. Remember what happened to battery life between the iPad 2 and 3 and that was the same sized battery.
Battery life is a spec that even Grandma can understand so Apple protects it strongly. If they know including something is going to drop that battery life down to as little as half the previous then they won't do it. After all, what good is an iPad Mini that you can only use for a quarter of a day or less unless you carry mophie batteries, a charger etc.