What will be the bandwidth required for streaming 640x480@30fps Video as UVC (USB Video Class)?
An uncompressed video stream will require:

$$640\times480\times(3\times8\text{ bit})\times30\text{ fps} = 27.65\text{ MB/s}$$

This is close to the net data rate I often encountered (~30 MB/s) for USB 2.0 with 480 Mbit/s devices. There are some devices around which reach more (thanks to Marcus Müller). So an uncompressed stream should be doable.

But you can also have a compressed stream as UVC 1.5 supports various compression formats:


  Video stream formats like MPEG-2 TS, H.264, MPEG-4 SL, SMPTE VC1, VP8
  and MJPEG


(Source)

I don't know the bitrate for those streams, but seeing that you can get a full HD stream over a 16 Mbit/s link, it shouldn't be a problem at all to get a compressed stream over USB 2.0.