The fact that "it may be possible" that humans transcend, does not imply that this will happen, and certainly does not establish it with at least 10% confidence.
Anyway, the idea seems backward. Some have argued that humans *are* a higher abstract mode in some sense that is not reachable by machines. If that is true, that doesn't refute the proposition either, but probably just means AGI won't be built, so the proposition would be trivially true.
But it doesn't seem to make sense for humans to become a higher abstract mode not reachable by machines, because if (a) machines can reach the abilities of humans, and (b) humans can reach an abstract mode, then it follows that machines can reach that abstract mode.