Question : uid to principal_id

In the older version, user was also some sort of 'uid'
sysusers.uid
sysmembers.memberuid

is it being change to principal_id in the new versions?
sys.schemas.principal_id

thanks

Answer : uid to principal_id

Yes, it is..
To confirm that, just run the query below:

select *, SUSER_name(principal_id), USER_name(principal_id)  
from sys.schemas