I tried to exit a delve on PC NA but get the message "... the destination is full" You can check out any time you want but you can never leave....oh wait
I will try that but all the npcs were dead around me and the bosses, it seemed that the instance was full......somehow entering the delve had allowed others to enter cyrodil and so I had to que in the delve.....I guess
When you enter a delve it seems that you leave cyrodiil so the population for your faction is now at its limit without you. You can join another campaign in imperial city or cyrodiil then leave the pvp areas or requeue for your home campaign.