You know how this works, right? A company has engineers. A company has IP lawyers. Whenever the engineers come up with an idea, no matter how small, the lawyers go to work seeing if it can be patented, whether or not the company intends to use that idea. This then becomes intellectual property of the company, and can be licensed, sold, given away or just ignored. Or even put into use. There are entire companies that make all their money buying/selling/licensing patents and suing infringers. Regardless, with a patent it becomes an asset, without a patent it is just an idea.
In summary, a patent application filed by Rivian doesn't imply that this is a feature they are planning for a future vehicle - it doesn't represent anything except that Rivian is making a good business decision to protect any and all intellectual property developed in house. That makes the company more valuable.