I judge this by trade value and Stephenson is the only one worth a 3rd; add Rissling.
As flawed as I think that approach to ranking prospects is, everyone has the right to rank them the way they want. However, I don't really see Stephenson as being worth a 3rd to most teams at this point. Maybe if a team was really in love with him and just didn't get the chance to draft him, but I don't think most teams would be willing to trade a 3rd for a guy just drafted in the prior draft in the 3rd round. They would most likely want to try their hand at getting "their guy" in the 3rd round of the upcoming draft.
A year or two removed from the draft, quite possibly (depending on how he plays and if a team wants to accelerate where they are in their prospect development cycle). Right now? Probably not.