There will be enough quests since judging by other MMOs that uses it for it's primary function, you'll mainly get quests like:

Kill 5 (small animal)
Kill 5 (small animal) 3 (not so small animal) 2 (insert humanoid type) 1 (boss type)
Kill 5 (bigger animal)
Kill 5 (even bigger animal)
Collect 1-5 (insert sparkling item near NPC)
Talk to (NPC) > (NPC) > (NPC)
Investigate (area) > fight (monster)
Kill 1 (insert sub boss) > (Kill 1 insert boss)
Deliver (Item) to NPC.

Those will loop infinitely, so they can make a large quantity of quests to last you for a very long time. So yeah it will take you from area to area and rinse and repeat the same style quests over and over while sprinkling in a dungeon here and there, that's what they're going for. They say you can do "a mix of things to level" but the primary, a.k.a main and efficient way to level is doing that.

Throw in the one time main storyline, and that's pretty much the level progression. The only true fear would be if they make the game "start" at end-game like MMOs nowadays which means the quality of progression from start to then may be very low.