Seeing as how it's coming to PS3 soon, I was wondering if there was anything I could do to get ready? What things should I begin to stockpile?

Iron ingots. LOTS of iron ingots. And some corrundum ones, as well.

If you're interested in building shrines to the nine divines in your basemant - an amulet for each of them.

If you want to grow ingredients for alchemy purposes - collect samples of plants you want to farm (I think the only thing that's not viable for growing is ninroot).

Other necessary things (goat horns, glass, straw, stone, clay, lumber) will only be added after you instal the DLC.