According to a report from Siliconera, it appears as if Disgaea Dimension 2 will change a mechanic that's been a part of the franchise from the beginning -- the item world.
The Item World is basically a way for people to grind out and power up individual items, alongside of the ability to level up your characters, reincarnate them, and level them up again.
Now, in D2, it appears as if it has been replaced by the "Item Sea," which allows you to sail across an ocean and battle pirates for treasure, and weapon items. Downloadable items have also been announced.
Disgaea’s Item World Evolved [Siliconera]