No query to migrate instances if new version defined from class definition template in GemStone Browser
If you generate a new version of an existing class by filling in the name
of the existing class in the NameOfClass field of the GemStone Browser's
class creation template (rather than by selecting a class in the class
pane), you do not receive the expected dialog box asking if you wish to
migrate instances.
Workaround:
Bring up a Class Version Browser and migrate instances explicitly.