In a bid to add replay value, the level you can grind to will be capped at each difficulty. Dualshockers writes:
Upon challenging the game for the first time only “Normal” difficulty will be available, with a level cap of 35. Meeting certain conditions linked to the story will unlock the ”Hard” mode, bringing a level cap of 65 and allowing more room for progression.
Upon clearing Hard mode players will unlock “Inferno” difficulty, that brings the level cap up to 99. And that’s not all, as clearing Inferno mode will unlock the Labyrinth of Chaos, an automatically generated dungeon that changes every time it’s challenged.
There’s also talk of items that will reset your skills but these will be hard to obtain. Due out 6th August in North America, Europe is still begging for a release date.