The pickpocketing tree has been heavily overhauled into the new Dexterity tree. There are still pickpocketing perks, but you will find new branches:
Dual wielding perks, some of which unlock the ability to move while using dual wield normal (and power) attacks.
Unarmed perks and the ability to make fist weapons that allow you to use different damage types (and enchantments) while unarmed.
Bow/Dagger attack speed perks.
Pickpocketing is now more generally useful. Most citizens will carry a modest amount of gold and jewelry and may have useful items like food or potions. Some of the richer citizens can carry much more gold and have enchanted items.