Was wondering that myself after seeing that Rivians at the First Mile event and in reviews didn't have the LiDAR sensors in my OP.
So I reached out to customer support and got this:
"Great questions and yes our Drivers+ will be updated via over the updates as at Launch it would be Level 2 but has the ability to go to Level Autonomy once we feel the vehicles are ready for that upgrade"
There was also this from a 2018 press release:
"The R1T will launch with a robust hardware suite with multiple modalities including camera, lidar, radar, ultrasonic and a high precision GPS coupled with high definition maps. This hardware enables
“Level 3” (hands-off wheel and eyes off road) autonomy for highway operation. Beyond the highway Level 3, the vehicle will have a range of self-driving features focused on enabling active lifestyles."
Change in Capability
Rivian Driver+ is standard on every vehicle we build. Delivering true hands-free
driving assistance along with our full set of safety features, the system continually adds functionality through over-the-air updates. By making Driver+ standard, our goal is to make driving safer, easier and less stressful for everyone.
They have 11 Cameras, 4 Radars, 12 Ultrasonic sensors.
These are enough to achieve the level of driver assistance capability they want to provide. Everyone who is doing driver assist currently are using some combination of those sensors above. Lidar is not needed hence they removed lidar once their scope changed. That does not mean future revisions to the system won't include lidar.