Yes, I'm migrating an existing plugin. I could just keep two versions of the plugin, but I wanted to avoid that. But maybe it's not really worth it...
(Also the question is what exactly "Zotero 7 will be out soon" means. Because that likely affects whether development should happen in the Z6 or Z7 branch of the plugin. My plugin is used in an instituational setting, and our IT department won't install beta versions...)