I was also thinking of picking up an inventory car at a steep discount, and still may, but it's pretty safe to assume you won't be able to do a full upgrade to the latest autopilot for long. Right now, the car is using mostly radar to keep its position, and that's fine for the current feature set. However, full autonomy would require being able to handle traffic lights, road signs, etc, and the car may not have enough computing power to handle it.
Now that Mobileye is out, Telsa most likely has to replace that chipset with something else like the Nvidia Drive PX2.(
Autonomous Car Development Platform from NVIDIA DRIVE PX2) It's way faster than even what mobileye has planned for the future and most automakers are switching over to that platform. IF that was the case, not only would the cars require new sensors but would also require the new chip and I'm guessing that would be a pain to retrofit. The latest and greatest autopilot chips/sensors will probably debut around the time of the model 3.
This is all just a big guess but if you REALLY want a self-driving car that can be part of the Tesla Uber-style fleet, might as well wait. However, it would take a few years to actually get there. I'm guessing at least 2 and maybe 3.
With this discount, and now the tax credits replenished in CA again, there's a good chance you won't lose too much money if you drive the car for a while and then sell it to someone else when new toys come out.
This is all just a guess but something to think about.