Okay, I'm not going to say Morgan will make the team or not because there is a good chance he could be the odd man out but I'll make an argument for Morgan.
#1) From what I remember, every time Morgan has stepped in the past couple of years, he's has done a decent job at LB, imo that always hasn't been the case for a guy like Smith. Morgan, imo, is a guy who can also play all three LBer positions and now you can add LEO end to the mix.
#2) Morgan has been a standout special teamer the past two seasons.
#3) Morgan has all the attributes you'd seek from a backup LBer: Versatility, Smarts, Quickness, Strength, and plenty of Athleticism. Carroll and Quinn both had good things to say about Morgan in recent articles, last week. He also has special physical attributes that the Seahawks love as well being a "lengthy" player at 6 feet 3 inches tall with 34 5/8 arms (2nd among linebackers), length that could eventually maximize his ability has a pass-rusher.
#4) I know he left a lot to be desired with his play vs. the Chargers. But that's to be expected when you take a 6'3, 225 linebacker challenge him to gain 15 pounds to play at a position where his athleticism can be a considerable factor but in a role where he still has to grow into and be comfortable. Note that it was Morgan's first time against a live opponent, in an actually game, playing at his new weight, starting at a new position with a new role.
I think people need give some players some slack around here, not everyone is going to pick up something and just dominate, there are learning curves, and plenty of time and practice to become a better player. Its like with the TEs... we have 1st and 2nd year players, its going to take time and plenty of reps before they start to get comfortable in their roles.