My theory for what this update comprises is thus: a new mode of trip travel, that gives you a sliding scale of participation by the car in the way that you apply power to drive. This is a similar slider to NORMAL/INSANE, or COMFORT/NORMAL/SPORT, or RANGE ON/OFF etc. etc..
TRIP THROTTLE will have three modes:
FREE
This is the mode that all cars are in today. Once the car gives you a suggested route and points out the status of the battery at the end of your trip, it throws you to the lions - or - you are free to do anything you like, including beat its prediction, follow its advice, gun the car until you stop along the highway, and worry as much as you want about whether you will survive or not.
GUARD
A green dotted line on the power meter indicates a "suggested maximum accelerator power limit." It shows the suggested throttle setting that you should not exceed if you want to get to your trip destination with reasonable, small charge to spare. You are free to go above this if you want, but it will remove charge from the battery faster, and consequently, the green dotted line will fall a little bit. It will sound an alarm to warn you of the excess usage. If you drive carefully and conserve more than you need to, the green dotted line may rise up, allowing you to gun it later
LIMIT
The yellow dotted line that indicates "accelerator power limit" shows up, and
prevents you from accelerating the car beyond a certain level of force. The position of the dotted line is exactly worked out to get you to the destination with reasonable, small charge to spare. The car will know about exceptionally steep uphill slopes along the route, and will allow temporary increases in power so as not to maroon you half way up the hill without enough accelerator power to get up it. If you do things to use up more charge, e.g. deviate from your route, elect to not maximise regen braking and so on, the yellow line may fall. If you conserve and regen as much as possible, the yellow line may rise. If the temperature drops, or weather turns against you and you have to use more power to proceed along the road, the computer will notice this (by examining throttle and road speed) and further limit the amount of accelerative force you can apply - but it will still enable the car to move.
In GUARD and LIMIT modes, you can use your heater and wipers, etc. as much as you want, and the computer will adjust the dotted line and/or change the amount of acceleration you will get. For example if it calculates that you should use no more than (say) 89W/mile to get to your destination, but the heater and wipers are using 7W, then it will only make 82W available to the motor - the end result being that 89W is still the maximum being used up. Savvy drivers will know to leave the HVAC off if battery charge is precious.
It's my opinion that the LIMIT mode would improve things enough to where you generally don't worry about range any more - and thus, Elon's goal is met. The car basically won't accelerate very quickly if you started a journey without enough battery charge to be able to gun it! That's your choice. But in order to get to your destination, the car might have to take some choice away from you.
