Rivian's potential deal with Amazon to sell its electric vans to other customers could significantly increase its revenues. This is because it would allow Rivian to tap into a larger market and potentially increase its sales volume. Therefore, this news is likely to have a positive impact on Rivian's stock price in the short term.

While Amazon's potential deal with Rivian could reduce its exclusivity over the electric vans, it could also support its investment in Rivian by potentially increasing Rivian's revenues and profitability. Therefore, the impact on Amazon's stock price is likely to be neutral in the short term.