It's funny, people dismiss training camp as if they just do it to get in shape, and no player evaluation occurs.
The two junior defensemen will probably return, in the case of Morin, he'd have to be better than a starting defensemen already on the roster to stick, because you don't want to hinder his progress by making him the 7th defenseman or giving him 10 minutes a night.
With Ghost, Alt and Hagg, how they play in camp will determine if they stick or go back to Lehigh. Given they just signed a 7th defensemen, and Grossman seems to be returning, it'll be very hard to stick, since like Morin, they lose all ties.
The difference is that they're only a quick car ride away, and Hextall can drive up and watch them himself and gauge their progress. I see pairings of Alt-Hagg and Lauridsen-Ghost (big stay at home with fast offensive defenseman), mirroring how they'll be used on the parent club. If they develop together, Alt-Hagg might be brought up as a pair, whereas Ghost might be brought up for Schenn, who seems to perform better with a mobile partner.
Given that Hextall wants to dump more salary (Vinny, Streit, are top candidates due to cost and age, Vinny hopefully this summer, Grossman depending on health), the progress of the kids at Lehigh may well make his decisions for him, if Ghost is ready, Streit becomes expendable, if Alt-Hagg are ready to step in, McDonald and Grossman become expendable. While people talk about trading Coburn, I think he's safe until Morin is ready, and that may be 2 more years.
I think Hextall is serious about developing the kids, he'd like to see them get hard coaching at Lehigh, then work them in and move veterans out over the next couple years. I don't think he's against veterans, just far more aware of the importance of keeping the salary cap in mind when planning down the road than Holmgren.