The system is already predicting what time of day you’ll arrive and how long you’ll stay as part of the normal trip plan.
More than that, they have data on what almost a million Teslas are doing every day, so if they put some effort into data analysis, they’ll quickly get not only how accurate the predictions are for any given leg, but also how people prefer to drive the legs - how fast are they taking each road, where do they skip a charger, where do they sit down for a meal or go shopping.
In principle they could even build a profile for you - this person likes sit down meals, but usually isn’t shopping in malls, that one prefers to drive straight through, and then personalize the navigation plan to match what you usually choose.
Obviously the plan won’t be more accurate than the weather forecast it is based on - but all they really need from that is “you might need another 20% for this leg” and if they overshoot it won’t matter much.