Possible Austin Martin scenarios if you sign Springer now
1. Martin busts (I certainly hope not)
2. They like Martin better at SS and move him there
3. Martin comes up and plays CF well just as Springer is ready to move to RF due to decline in speed/range
4. Martin progresses rapidly, both he and Springer are awesome CF options in 2 years and you trade one of them
No need to worry about where Martin will play at this point