Today the ImageJDev team is releasing the fourth beta of ImageJ2, version 2.0.0-beta4.
ImageJ 2.0.0-beta4 is a "beta"-quality release, meaning the code is not finished. The design is more stable than before but still subject to change until the final 2.0.0 release. It is recommended that people continue to use ImageJ v1.x for critical work.
Download using the link below, or from the Downloads page, which also has a timetable for future releases.