Not sure there is a limit
Not sure there is an actual limit but the practical limit I would say is 3. However, you are trying to connect 3 HIDs (Human Interface Device) up. There very well could be a limit of 2 HIDs. There may be a way to disable the remote control on your BB and just use the bridging part. If so, that might allow you to connect all 3.
I have used my Mini-KB, Bluetooth stereo headset and bridge at the same time. I was touchy.
OS 2.1 will allow bridge VIA WiFi. That is going to be nice.