There's going to be the people who care not for the storyline and race through, if not outright skip the cutscenes, just to unlock their latest trials and dungeons to run.
There'll be the people who sit back and soak in every cutscene, talk with every NPC between each main scenario cutscene (guilty of this) and generally take their sweet time.
There'll be the ones that race to the new job giving NPCs as soon as it's available to them and go back to Haukke and start levelling that.
There will be the crafters and gatherers looking to earn their tomestones while others are busy with the main scenario.

So even if everyone has a linear questline without much branching (I'm suspecting no branching tbh), there's player based branching off individual interests and playstyles.

That being said, Coerthas and Ishguard will be so packed on day 1. I do not foresee the zones stability lasting long!