Future Tesla Model 3 owners might be able to access their cars using some sort of card, if we are to believe what we've seen from some video stills.
In the video we referenced, you can see Doug Field, Tesla's Vice President of Engineering, entering the vehicle and depositing a booklet into its center console. It is believed that this booklet houses a small RFID card that works just like a key fob in a hands-free keyless entry and push-to-start car. It's all based on proximity rather than the need to unlock the vehicle by hand.
The same booklet can be seen resting in another Model 3, also believed to house the same key card used to grant access to the vehicle.
Concerns of how to remotely unlock the vehicle have become apparent. We know that historically Tesla has used cellular data to provide Over-The-Air (OTA) updates to its vehicles, so it's possible that an authenticated user with a smart phone could use their Tesla app as the sole means to unlock their car remotely (instead of pressing a button on a fob). If that is the case, what happens if a vehicle or phone does not have cellular service in a particular area? This is still a very real issue for rural America, and even some suburban areas as well. Currently, the Tesla app utilizes Bluetooth, however the driver would need to be within range in order to utilize this functionality. But that's also assuming that the driver needs the convenience of not having to walk up to their car, and Tesla is a company built on a foundation of convenience.
In all fairness, this could also be a method that Tesla uses to loan out keys to employees. They might simply be checking out a temporary key card in order to drive the vehicle.
Though no official word has been made regarding this yet, we may be seeing more details in the coming week. Tesla has its first Model 3 event occurring on July 28 where it reportedly plans to issue its first 30 production vehicles before sharply increasing production numbers. During this time, we might learn a lot more about the vehicles than just the speculation we have today.