* can beagleboard act as a host and device simultaneously on different
Yes, on the BeagleBoard-xM, you can use the OTG port as a device port and the four host ports as host ports.
* My aim is to achieve 60fps @ SIF for each camera, does this sound
realistic? (I am not sure how to calculate whether this is possible or
The maximum throughput per endpoint for USB high-speed, non-high-bandwidth isochronous transfers (used for streaming audio/video) is 8 MB/sec, if that helps.