In the case of a production DBA then a possible career progression might be to a Database Manager.
For a development DBA / database professional who wants to pursue a development career the options are much the same as for other developers. Many development teams don't necessarily have a formal DBA role, they may just have developers with many different skill sets and specialisms of which a database specialist (aka "DBA") is one example.
I don't think DBAs have limited scope in their careers. It's just that the term "DBA" has a very limited meaning for many people - and one that probably doesn't do justice to all of the people and roles sometimes labelled with it.