First do secondary admin then all PSNs' and finally primary admin.
Yes, the moment you'll do upgrade, they start forming new deployment.
http://www.cisco.com/c/en/us/td/docs/security/ise/2-1/upgrade_guide/b_ise_upgrade_guide_21/b_ise_upgrade_guide_21_chapter_00.html
Regards
Gagan
ps: rate if it helps!!!!