Is it possible to create a "Meta-Forum" view when using organic groups?
It is very easy to build such of "forum" using Views. If you are using Organic Group Access, the view will be automatically filtered and only the content accessible to the user will be displayed.

Note that the OG Forum module has been abandoned due to security issues and should not be used. Depending on your requirements, it might be easier to simply use standard Views for the group forums (after all, a forum is nothing more then a View of taxonomy terms attached to a View of nodes).