It's not a question of upside.
It's a matter of fit within the system.
Korchinski's ceiling is probably a #3. I think based on everything we've seen, that's a fair peak to set for him. He's never, even in his draft year, shown that he can be a true top pairing guy. But currently, he's a #7.
Vlasic is already a #2, and Rinzel and Levshunov have top pairing upside. Hell, Rinzel might already be one.
Kaiser and EDM are pretty much already #4 type guys.
Crevier is a #6 already.
So let's say, in a couple years, Korchinski doesn't quite hit his ceiling but he ends up a really good #4. By then he'd still be behind Vlasic, Rinzel, and Levshunov on the depth chart. And at most, be on par with Kaiser and EDM. Maybe even Crevier elevates to that level too by then.
You're then in a position where Korch is playing bottom pairing minutes, and getting zero PP time because Rinzel and Lev are running both units. Does that work for the kind of player he is? I don't think so.