On topic, Yoshi said that he played many games over the course of 1.0 being re-hauled. If you have played guild wars 2 you would know exactly what they plan to do if a zone it over crowded as someone has already mentioned. You will be put in a overflow area. It will be a zone that puts all characters from all worlds in this overflow. You will then enter a queue in which you will be ported into the your own world zone. This is based on who was before you.

I believe this is truly how they will do it because if you have played guild wars 2 you will notice that "FATE" or Full Active Time Event which is being planed to be test in the beta form is exactly like a dynamic event in Guild Wars 2. If they took this from Guild Wars 2, i am sure they were bright enough to bring the queue system too.