Andre went a different direction creatively than Big Boi (both in sound and the content of lyrics) then seemed to lose his thirst for making music in general, particularly rapping. He's done quite a bit of acting, fashion shit and the like in the mean time.
But he's done quite a few features the last 2-3 years and they are allegedly making another rap album. It''ll be interesting to see what they do; Big boi is still on that smoke weed / pimp shit vibe he's always been on and Andre started moving away from that really after their first album.
It's kinda hard to listen to old Outkast for me; Andre's angry slut shaming on ATLiens sort of ruins the album for me.