Yeah and I am convinced that most teams will end up keeping a 3rd string dev QB in the future
Well in the recent past 2014 SB champs NE carried 2, 2013 SB champs Seattle carried 2, 2012 SB champs Baltimore carried 2, 2011 SB champs NY carried 2, 2010 SB champs GB carried 2.
If you've got a SB caliber QB it just doesn't make a lot of sense to waste the cap money or extra roster spot on the backup QB position when those resources can be better spent elsewhere.
If you don't have a franchise QB, you probably do need to use some extra resources trying to find one but you're also not likely to be competing for a championship...