I think Rivian will take the startup approach and pack as much density into their battery, even if it means sacrificing a large chunk of their margin. The r1t is supposed to have a weight of 8500 pounds[0], so I can see a 150-200kwh battery being packed in there on the Max pack to achieve that range.
0: https://insideevs.com/news/536753/rivian-r1t-gvwr-heavy-duty...