Hmm So if your already thinking about things like achievements maybe 1.3 is.......Never-Mind ^_^
I would really like to see one when you:
Defeat every kind of enemy
Place 5 of every single block in the game (Hardcore XD)
Drink one of each potion
Spend 150 minutes underwater
Have every pet...
My friend and I had an amazing idea for 1.3! Weapon variants like the cursed nimbus rod or ancient terra blade or something they could just add permanent bonuses and look different hence the variant bit