Originally posted by Qubo Night Owl:

Do you need to start a new world for it to have the various things they have added to the game since the initial early access release.

Only if you have already explored the biomes that were added since you played; if it's already discovered, it doesn't (re)generate properly.

That being said (and assuming you need to make a new world), you can use your character to snag your gear and any materials you've already farmed through the magic of world-hopping. Log into your old world, grab anything that isn't nailed down that fits into your inventory, then log out. Create a new world, log into it with the same character, build chests, and dump your inventory. Then log out, log back into the old world, grab more stuff... lather, rinse, repeat until you have everything you want/need to start out as strong as you were when you last played.