Absolutely. If I don't have a backup or I want to upgrade the backup position -or even the 3rd QB position - then yes, I would definetly draft one if I felt like that was a need for the team.
This isn't about just the 7th round. Teams draft QBs as backups in earlier rounds than round 7.
Dave Ragone and Stefan Lefors were drafted in later rounds this year as backups. Lefors MAY become a starter one day. But it isn't very likely. Ragone could, but is less likely than Lefors IMO. But both can be caretakers of an offense should a QB go down for a few games. Coaches and GMs know if they are getting a QB who can win games for them with their own ability or if they are simply getting a "caretaker" for their offense should the starter go down.