I'm not an orthopedic surgeon, but I am studying to be one. I can tell you guys/gals with certainty that if Luck has a mild subluxation without structural damage, that signifies that at the GH joint, where his glenoid cavity of the scapula bone and humerus connect, the humeral head became mildly dislodged from the joint (this picture should help), and slid back into place soon after

Now, the real concern is with the labrum, which surrounds the glenoid socket, where the humeral head rests. If the head is severely dislocated, there is a chance for a labral tear, which can be visualized in the picture below.

However, in Luck's case it seems since there is a mild subluxation, the labrum is only "bruised" or contused due to impact from the humeral head moving around a little bit. Hence the "bruised" and "sore" coachspeak we've been hearing about from pagano. So yes, I suspect that this is indeed a minor injury and there shouldn't be any residual effects on the shoulder long term. I fully expect to see Luck out on the field on Thursday!

On a side note, I hope this injury has altered Luck's mindset a little and made him look for the shorter throws first before looking for the deep bomb. Think about it: the more plays you call with 5 & 7 step drops, not only is Luck going to get battered more, but the O-line will be more fatigued with having to protect for longer periods of time each play! It's common sense Pep, use it!