Green Card vs Citizen

[malwa]

I need some advice for filling my immigration papers.I am indian citizen.

My husband is an American green card holder going in for finger
priting next week.

Should he apply for me (his wife)under his green card.
Will the file move from the green card pile to under the citizenship status automatically
or will the processing time still remain as of a green card .

My question
Should he apply for me now or should he wait for his citizenship.