From what I know, you can continue using it but you cannot extend it. For F1
re-enter US, you'll have to use AP as you cannot get F1 visa issued any
longer for immigration intention.
I have the same situation. After I submitted my I485, I kept using my OPT to
work until I got my EAD card. Now I am using my Combo EAD card because my
OPT card is expired.