TShark and Rotating JSON Files

This is more a tshark questions. Never tried myself, but have you tried with the -b flag?

$ tshark -h
...
Capture output:
  -b <ringbuffer opt.> ... duration:NUM - switch to next file after NUM secs
                           filesize:NUM - switch to next file after NUM KB
                              files:NUM - ringbuffer: replace after NUM files
...