I'd classify Cherryh's Foreigner series more as a form of "Metaplot Novel" in this schema. There are only 2 POV characters in the whole series so far, one of them introduced as a young child, and a handful of ongoing storylines that each get some time as the main focus of attention then recede for a while, then come back to the center. The trilogy structure originally tracked these changes of focus pretty closely, but not so much anymore: I wouldn't actually consider them trilogies at all any more, except perhaps for accounting purposes. The story just continues from volume to volume.