CNAM isn't going to be implemented on Google Voice. With the increasing proliferation of non-POTS phone numbers (mobile and VoIP), the CNAM databases are no longer sufficiently useful as a source of caller names. Many mobile and VoIP carriers simply don't feed their customers' names to the DB providers. In addition, carriers have to pay to both feed their customers' names into the DBs and to "dip" or look up the names. Since GV is a <mostly> free service, CNAM would add extra cost for something that is of limited value.
This is unrelated to any Hangouts/GV integration plans.