I don't think Shortell will switch positions ever, he is a QB (IMO).
This is a situation that almost every single good program in the country has.
I don't think it's really that complicated.
(1) Gray will be REALLY difficult to beat out next year.
(2) Shortell and Nelson will be (most likely) competing for the backup position. If Nelson is further along than Shortell, I don't think Nelson RSs. In our offense, there is a really good chance that Gray will need a breather and/or miss some time.
(3) If Leidner stays at QB right, he will RS. If he moves, it will be to either TE or DE (my opinion). Either of those are possibilities, but I think he will be RS and then evaluated. Kill liked something in the way he threw the ball, so i'd imagine that Leidner will spend at least a year taking snaps as a QB before we decide to move him or keep him there. Keep in mind that if Nelson doesn't RS, they won't even be in the same class.
(4) Foreman, I know very little about. He actually threw the ball better than I thought he would in the practices and spring game. I wouldn't be shocked if he gets moved though because he is a pretty athletic kid. However, his role could definitely end up being (in the future) as a sort of wildcat hybrid type QB that takes some hits off Shortell/Nelson. Northern Illinois used a kid (Jordan Lynch), who was a QB and ran the offense, but would come in to sort of spell Harnish (he wasn't their backup, he was like an advanced wildcat). They would usually run with him and he was a good runner, but he was a QB and a real threat to throw. This could be Foreman's future....but I don't know, he might be the best of the bunch...who knows.
Lastly, I don't think it's really wise to make broad judgments about players who are freshmen. I think it's impossible to tell what kind of QB Shortell is going to be. A true freshman QB is going to struggle a ton, it's a completely different game, much less a true freshman QB who is playing on a team that is struggling. So I wouldn't prognosticate about Shortell's future based on the Michigan game.