I feel like the BIG surprise feature could be one of these 10:
Lauryn Hill
AZ
Cormega
Drake
Kendrick Lamar
Q-Tip
Andre 3000
Jay-Z
Lil Wayne
Jay Electronica
AZ and Mega were on the last album. It wouldn’t be much of a surprise more as it would a pleasant continuation of their reforged musical collaborations
Lil Wayne was on Distant Relatives and Nas was on The Carter 4. Them working together wouldn’t be too huge of a stretch.
Jay Electronica and Andre 3K would be HUGE surprises as fans have been begging for an official collab with Nas for years. Nas and Andre worked together on Lloyd’s You remix and of course Jay Elect produced on Untitled but to have a REAL song with either one would be manna from Heaven.
Nas and Lauryn Hill together again would be insane. ESPECIALLY if Lauryn were to actually drop some bars and not just sing a hook.
A Kendrick or Drake feature would be instant radio baiting. A single/video with either would be guaranteed to chart highly.