Xojo is there and you can download it. You can read reviews about it at the Xojo Developer Magazine, Bob Keeney's Briefs and a few more including the Real Software Blog.
Xojo is a great release. It finally moves forward and brings the new IDE and switches the license model. Also we will enjoy the new books/manuals and the new cloud feature. Also Feedback app is updated with a new look. We are happy about all the bug fixes in the framework, but still fear that some changes/bugs may corrupt projects. We'll see how the release will do in everyday work.
Plugins for Xojo
With Xojo a new plugin file format is introduced. But older plugins still work. On the long run you will want to use the new format as it loads quicker and the files are smaller. And as MBS plugins are available in both favors, they have not the same content. The rbx files still contain the PPC code which is missing for the new xojo plugins. And our xojo plugins will be the plugins which will include 64bit some day.
Whether you use rbx or xojo format plugins doesn't really matter. Just make sure you use recent plugins. 13.1 is okay, but 13.2pr4 is better. We fix bugs as soon as we know and we hope everything is right for Xojo so far.