Based on what we know from people who have been digging around in the AP software, it seems likely to me that automatic overtaking of moving vehicles (using the rear-facing cams) is a good bet for a major feature release in 2018.
Integration with navigation to enable on-ramp to off-ramp would also seem possible, now that they have their own nav solution, but less likely in 2018. Look how long it is taking to get the nav rolled out globally. (Nice to see some measure of caution here, tbh).
Showing traffic signs on the display would be a "quick win" IMO - stop signs, traffic lights, school areas, etc. - but Tesla may not consider this to be safe for drivers who would probably expect the system to react to the signs while AP is enabled.
Any thoughts of L3 can probably be put to bed until Tesla have a fool-proof solution for dealing with immobile lane obstructions (fire trucks, parked cars, etc.).