I have a feeling these orders are going to pile up. Many companies could be at a disadvantage at some point if this takes off. Tesla will give preference to early adopters for further Truck/Tractor sales. I would imagine they could also leverage this with trailers that sport solar panel on the roof to help recharge a battery for refers and even put regenerative braking on trailer wheels.
I have so many good ideas I wish I could share with Musk concerning this industry, too bad he is impossible to reach by us simple folks.