As other people have pointed out, it's simply too early to tell if this will be your son's passion in life.
But that doesn't mean you shouldn't support it and nurture his interest.
As a toddler, the best way to do this is to gradually expose him to a wider variety of construction vehicles, and provide increasingly detailed contexts in which they're used.
As CreationEdge mentioned, pointing them out when you see them, and bringing your son to places with a variety of vehicles at work, is a great way to nurture his interest.
Rory's suggestion of "How its Made" and "Mega Machines" (we watched "Mighty Machines", which was geared for young children; I'm not sure if that's different from "Mega Machines") are great choices for TV entertainment, but, as with all TV entertainment at that age, it is best if you watch with him, and actively engage him throughout the show with questions and discussion.
Depending on your area, local farm shows, town fairs, and conventions might be great activities where these vehicles can be viewed, and possibly even directly interacted with (our annual town fair includes a section of modern farming equipment where kids can climb into the seats and play with the controls).
As his verbal skills grow, talk with him not only about the vehicles, but about how they're used, and why what they do is important. Talk about the people who drive them. Talk about the people who design them. Talk about the people who build them. The goal is to show him that there are lots of different ways people can be involved in these cool machines, which will help him decide which areas he might be most interested in.
There are, after all, some very different careers that all work directly with these machines. Construction crews, mining companies, engineers, assembly line workers, sales representatives, etc., all have very different roles, but work with the same machines. Discussing these different jobs with your son could open up entirely new areas of interest.