With AP you need to be aware and in control of the car. You're the driver. You can't take a nap. You're "supposed to" keep your hands on the wheel.
With SA, the car is in control. You can do whatever you want. Level 3 will be something like on-ramp to off-ramp, and if it cannot do that, it will give the driver sufficient notice to resume control of the car.
There is no AP2.0 yet. It's just speculation that there will be, and it's a term people came up with.
AP is Level 2, SA is Level 3/Level 4. (
Autonomous car - Wikipedia, the free encyclopedia <-- decent summary under definition, though some organization uses 4a and 4b to decipher cars that can do P2P and cars that can't)
For all we know: AP2.0 could be automatic lane changes. AP2.0 could be rear-radar to avoid being rear ended. AP2.0 could be cross traffic detection. AP2.0 could be a pack of monkeys in the trunk. AP2.0 could be 8 cameras and everything necessary for SA, and SA will come in 3-5 years. No one outside of Tesla knows.