Uh, I don't think 240/305/420 with 20 HR's is that unreasonable, IF he's an everyday player, making 650+ PA this year. FWIW, PECOTA has him pegged at 18 HR in 469 PA and a 269/329/468 line, which would damn nice to have--and that's just his "average" season according to them.
I'm not sure I get the logic here. According to this, I should not "expect" an event that is "very possible" to occur. If something is "very possible" to occur--is that thus likely to occur? It's semantics I know, but I think the two terms are closer than your statement suggests.