Because they'd be using 'is' instead of 'instanceof'? That just really doesn't strike me as a meaningful difference. Hell, they already have a lot of way more

Because they'd be using 'is' instead of 'instanceof'? That just really doesn't strike me as a meaningful difference. Hell, they already have a lot of way more crazy changes (the radically different lambda syntax, different function signature, functions outside classes, extension functions, etc). By your reasoning they're already way past the point where "it's 'easy' to switch from java to kotlin".