How many Bluetooth devices could I have connected to the Surface Pro at once?

I'm pretty sure it will be packing Bluetooth 4.0... so how many devices can I have connected at once? Is there a limit? Surely, there must be. (Yes there is, and don't call me Shirley :p)

I want to pick up a Logitech bluetooth keyboard (K810) and then use my phone as a touchpad... so it would just be two devices.