Elon Musk's new Master Plan (Master Plan, Part Deux) requires an extension of its vehicles into different classifications, including heavy duty trucks and buses. Without a doubt, carbon emissions worldwide would fall steeply if the general car customer transitioned to a tailpipe-free electric Tesla, however that is not what Elon Musk is after. His objective is a full frontal attack on carbon emissions of all kinds including a Tesla Semi. His goal is for nothing less than a world that no longer uses petroleum products to power its transportation framework, even on a commercial transportation scale.
Musk explained that in addition to consumer vehicles, there are two other types of electric vehicles necessary: heavy-duty trucks and high passenger-density urban transport. These vehicles are currently developing at Tesla and should be ready for product introduction in the near future. They believe the Tesla Semi will deliver a substantial cost reduction in the cargo transport, while helping drivers’ safety and making it exciting to use.
The issue with electric trucks today is that the batteries need to so large and heavy they would take up a significant part of the space accessible for pulling cargo and would be prohibitively costly. We can expect the Tesla Semi won't have a range extender engine. How Tesla will make an electric tractor that can pull substantial loads lengthy distances that is cost competitive, is unclear. If Elon says that is the thing that Tesla will do, we can be almost certain it will, eventually.
We know maritime freight vessels are a part of the worst polluters on the planet.
Musk likely has an arrangement for them, as well
... possibly a piece of Master Plan # 3.
As of April 2017 - there are the 8 Tesla vehicle programs in the works:
⍟ Model S
⍟ Model X
⍟ Model 3
⍟ Model Y
⍟ Roadster next-gen (placeholder name)
⍟ Minibus (placeholder name)
⍟ Pickup truck (placeholder name)