Drake is a no brainer... yet to make a Coachella appearance. He will likely close outdoor theater one night
also likely or possible..
Eminem (headliner doubtful but he would get main stage i hope not though)
Kendrick Lamar (if no Drake next choice for popular new rapper) RiFF RaFF (daytime set and cameo with Diplo/Major Lazer)
LL Cool J (oldschool appeal, touring again) Chance The Rapper (for the pitchfork groupies) Rick Ross (not sure but he would fit the bill if Drake doesnt come out) Big Sean (same as above)
Goodie Mob (possible) Schoolboy Q (gaining popularity) Dom Kennedy (releasing a lot of material in 2013) Dizzee Rascal (international appeal, new album)
unlikely but possible rap/rock hybrids Rage Against the Machine (oldschool appeal)