It will be faster.
When the temperature rises, this means that the molecules move faster.
Let's say we have a layer of water, and a layer of ethanol on top, divided by a barrier. If we remove the barrier, some of the water molecules will move up into the ethanol layer, and vice versa. This will continue untill there is a dynamic equilibrium, where just as many water molecules move into the upper layer as move out. The same goes for the ethanol molecules.
With temperature rising, this equilibrium will be reached sooner, as more molecules per time unit will cross the dividing line.
So with higher temperature, liquids will mix (diffuse) faster.