King's scoring dropped from 13.6 to 11.1 points a game from his sophomore to junior season following him being named the Pac-12's Comeback Player of 2016. Most of this was due to a dip in shooting percentages, fewer perimeter opportunities with Derrick White and less open shots without Josh Scott.
King has not hired an agent according to BSN Denver's information so he essentially is just testing the water and as ESPN's Goodman notes, "A bunch of these guys will drop out and withdraw once they realize they aren’t being invited to combine. Some doing it just for attention."
It's highly likely King will be back with the Buffs next year but this something certainly to watch out for. The early entry deadline was April 23, and college players have until 10 days after the draft combine (May 9–14) to withdraw from the pool.