It looks like the last version of WPILibJ is 2017.1.1. So, if I want to build with Maven, I would need to build WPILibJ myself or have the standard plugins and then create a local Maven repository or add a static jar dependency?
Where are you looking at? Everything is located here, including the latest release.
http://first.wpi.edu/FRC/roborio/maven/release/edu/wpi/first/