Yep, although it's generally pretty quick to catch up cause you get armory bonus(the full one, currently it's 50% for these levels but after expansion it's 100% cause it's not the cap anymore)+earring(as long as you preorder which you should anyway since it's an expansion, and you can "preorder" the day before release). Last expansion I did HoH on DNC and only took a few hours to get to 70, then you just level normally. I assume this time I'll do Bozja if I end up playing one of the 2 new classes, although I've never done Bozja for leveling(all my stuff was capped a couple of weeks in ShB). If you have sidequests you can also turn these in, it's not much though like turning 30 sidequests is about 30% xp, but that makes the first leveling roulette get you to x1, which opens access to Bozja(need to be 71 to enter). You can complete them before the expansion and just spend 3mins to turn them all in. If you don't you usually have to do alliance roulette too to get there or do an actual dungeon run.
I assume for Bozja you'll want to prepare some Lost Actions though to make it easier. It's unlikely there's gonna be any tank in Bozja so looking into a way to tank FATEs is probably high priority, since you'll have plenty of DPS(Reavers) and healers(Sages).
If you want to play the new content asap though you're better off playing an existing class and switching after. I'm waiting for the live letter to decide myself, plenty of classes I'm interested in so I'll probably leave the new classes for later, thinking MNK first if they rework it(not sure if they'll have finished the rework or if they're planning to do it in 6.1 like they did Ninja in ShB) or SCH.