Here is my calculation:
A couple of things:
1. The cap holds after the rookie contract are either 200% or 250% of the previous salary (Depends on the average league salary!)
2. At least 12 roster spots count against the cap. Free roster spots are charged with a cap hold of the league minimum.
3. 2nd round draft picks don't have a cap hold.
It is a strong possibility that the salary cap and the luxury tax treshold will increase a couple millions over the next years but I think we have to be activ after this season! This will give us the better financial flexibility to have a stronger roster.