He's 25 years old and will be 31 when he's eligible for free agency. I doubt Elias is worried about holding him back to get an extra year of control. The missed season has put a lot of what Elias typically has done in question.
If Baumann doesn't get hurt, I believe he would have gotten that call up instead of Kremer based on what I heard about them at the time. While Kremer does have a starting spot to lose at this point, I think Baumann could end up the 5th starter as well in this rotation if he's healthy and pitches well this spring.