SCENARIO 1 - OP dies after his aunt.
as above
SCENARIO 2 - OP dies before his aunt.
On OP's death, and, under the terms of the will, his child becomes the beneficiary on reaching his/her majority. {edited for clarity]
SCENARIO 3 - OP dies after his aunt but was alive when she died but probate is not completed.
no comment
SCENARIO 4 - OP dies before his aunt and the will makes no provision for OP's child.
The OP's child becomes the beneficiary on reaching his/her majority as the bequest follows blood-lines. Adopted children are treated as blood relations in this scenario.
SCENARIO 5 - OP dies before his aunt who dies intestate.
As Scenario 4, above
All on the assumption that "aunt" means blood relation and not the spouse of OP's blood-related uncle.