It's hard to speculate on just about any of this without knowing firsthand the level of development of guys like Clark, Kramer, and even Zack. Not out of the realm of possibility, given the relatively modest ceiling of Morgan, that one or more QB's have at least closed the gap considerably in the last 12-18 months.
The one thing I would slightly disagree with here in some comments; if indeed the gap isn't massive from Morgan to QB #2, and Morgan starts out playing subpar football, I don't think it would take a MAJOR injury to make a move.
With the returning starters this year, particularly on the OL, obviously the window for a big season is now. Can't sacrifice any games out of loyalty to a guy who had a good season almost 24 months ago.