The 2nd PBEM tournament is still ongoing, and I imagine that when it is over, perhaps when it is approaching the finishline, interest will be gauged for a 3rd tournament, and if a suitable number are interested in participating (not forgetting the significant effort involved in getting it started and keeping it organized), I would be very surprised if we don't see one
At that point, announcements are made, and interested players announce their interest in participating; in the 1st and 2nd tournaments, there were no special requirements for participating, other than having the time and inclination to take part
