All of this is true. However, in HIS best interest, staying AT LEAST two years can only benefit Kofi. He will be matched up against guys with his size and skill level who CAN shoot an 18 footer. Time is only going to make him better.
If we're being honest and unbiased about what's in his best interest, then it is in his best interest to go if he believes he'll be among the top 40 picks, and definitely if he's in the first round. He is already 20, so the clock is ticking on his stock. Seeing what is currently happening with Ayo, and the potential for his stock to be lower this year than it was last year, should only make this more clear to us fans.
Kofi is a MUCH better prospect than Bruno Fernando, both size- and skill-wise, and he went 34th last year. Kofi may be 15 years late in terms of NBA big man trends, but there are still tons of non-shooting big men getting tick in the NBA. Free throw shooting tends to be what teams look at more for projecting shooting ability anyways (amongst players that don't take tons of jump shots in college), and Kofi has been very impressive there so far. He doesn't appear to be hopeless with his shooting touch, unlike a Capela or Deandre Jordan. And if Kofi can continue to block shots like he did against Michigan, then GMs will have an easier time overlooking his mobility on the perimeter.
Non-shooting big men are the NBA's running backs. Are they getting giant contracts anymore (relatively)? No. But would a team like the Celtics or Raptors love to have a serviceable big that can rebound, block shots, and hit his FTs for ~$1.5 million/year for 4 years, with the upside for more production down the road? Of course they would.