Could Ms. Leigh Bardugo get the rights, or IP, back from Netflix? 

According to this source, it will take 10 years for Ms. Bardugo to reclaim the rights, or IP, of Shadow and Bone from Netflix. 

As you can see from this Wiki,  Ms. Bardugo sold Netflix Shadow and Bone's IP before January 10th, 2019, the date in which Netflix ordered the first season. This means Netflix still legally owns the rights to Shadow and Bone until January 2029, despite the show's cancellation this past November. 

If you have been wondering when Netflix's grasp on Shadow and Bone will cease and be rightfully returned to Ms. Bardugo, the soonest it seems it will be is 2029--5 years from now. Whether or not the casting is guaranteed or not, that remains to be seen. 

Hopefully we can save the show before then before the five years are up to avoid potential recasting. Until then, keep fighting!  

NMNF, 

Cryptical_723