I think there's a close to 100% chance that the tombstone will be alluded to, because even if Eliezer DIDN'T know about it before, he will by the time the story ends (because I will have questioned and informed him about this), and after that I just can't imagine him making such a terrible mistake as to NOT include the tombstone's quote.
I do think a simple bet of "did he already plan this?" is feasible. We can just ask him. (I put odds at 75%).
(By "close to 100%" I mean maybe 95. I can think of scenarios where he hadn't originally planned for the tombstone and where it would be hard to integrate it)
Here's the new thread for posting quotes, with the usual rules: