You think they'd push any of these guys into the bullpen?
Obviously, if any one of them is not healthy, he won't be in the rotation. But between these seven, and the three starters they'll be adding to the roster in a few weeks (Appel, Lively, Pivetta), they've got ten young starting pitchers - all of whom still have options. I really don't see them moving any of these guys to the bullpen; they'll build a rotation out of the best/healthiest performers in the spring (with or without Hellickson or some other "veteran" to "anchor" the rotation), and option the rest to AAA, where they can continue to develop.
It's not as if modern bullpens even have a true "long man" role, where a young starting pitcher could get three-four innings of work on a more-or-less regular basis, an occasional spot start, etc.. Anybody who's added to a contemporary bullpen is going to be used in the "one-inning, far too frequently" role, until they lose effectiveness. It's just the way relievers are used today.