I really don't see the benefit of disclosing the number of preorder reservation holders publicly, and am doubtful that Rivian will do so prior their estimated production date.
I can't help but feel that currently Rivian is like a snowball rolling down a mountain and with each passing day is picking up more preorders, and it's in their favor above all else to keep that number private.
Honestly no matter what the actual number is it will either be lauded as being "too big" for a fledgling EV startup, or "too small" in comparison to other current main place auto manufactures with electric vehicles already to market. But in all seriousness Rivian can use this to their advantage and spin the numbers whichever direction they want depending on whom their target audience is.
Each preorder event nets more eager buyers and this carries with it opportunities for Rivian to go to the next interested partner and then disclose how many people are waiting in line for their vehicles. But if they told us now, the cats out of the bag and now everyone can chime in on what they think of the numbers, and it's just kinda out there. Either too big or too small, but all of it should be taken in context and of course that context is ever changing i.e. Amazon, Ford, etc... Who knows who else will jump on board?
I think the number will be higher then what people would expect in most cases. The EV revolution is upon us and I am confident that Rivian is seeking the help of whomever is in support of their mission and vision of transitioning to renewable and more sustainable transportation models.
Tesla comparison are always amusing, but I think Rivian is doing enough to differentiate themselves form the pack of other EV makers out there.
Only time will tell...