Tim, I assume you meant this as a nit-pick rather than as a substantive criticism. Substitute "if you accept option 3 of the simulation argument".

If you think this objection is substantive, I expect you to lower the probability you assign to reaching post-humanity and to posthumans wanting to run simulations. (The "ancestor" part in option 2 should be struck out; ancestors are only a small subset of the kinds of agents posthumans might want to simulate that would be more primitive than posthumans.)