You have join preference if you are ranked?

[Jevmen]

The limit is actualy 750 playes, i gess if the players are over the limit the game will be slightly lagged and if the players are over the limit by a lot the skyblock will be closed for other players.
If that happend you will need to spam the NPC to enter frist when someone leave or you enter a queue?, if the answer is the queue, ranked players will join before unrankeds?

 

[Zed]

If Skyblock is full then those with ranks can still join. The limit is increasing rapdily it's just a safety precaution.