Zotero will work the way it does with Chrome now: there will be a plugin that integrates with Zotero Standalone, which will continue to be developed using XULRunner.
I think this will be good in the long run--Zotero is complex enough to merit being its own application, and separating Zotero and browser plugins will make it easier to migrate Zotero off XULRunner at some point, if the developers choose to do so.
I think this will be good in the long run--Zotero is complex enough to merit being its own application, and separating Zotero and browser plugins will make it easier to migrate Zotero off XULRunner at some point, if the developers choose to do so.