If you have an IFR-certified GPS with WAAS in your panel, you’re already equipped to take advantage of the bulk of what NextGen has to offer GA today. There, don’t you feel better?
The reason is that NextGen is a fat catch-all for a host of technologies that mostly target airlines and major airport ground ops. Biz jets will reap some of the airline-focused bennies, but for the bulk of GA, NextGen boils down to RNAV instrument approaches and ADS-B. And it will likely remain that way for the next decade at least.