[IMRight]

Just because it isn't mentioned doesn't mean it was skipped.

It wasn't just "not mentioned". There is no gap in the story where you can infer "oh, they must have consumed another cup of wine during that textual pause". No, they sang the little Hallel (which immediately preceeds the fourth cup) and "went out into the night". Christ also said He would NOT drink again right after He had the third. Did He forget and drink the fourth?

[Invincibly Ignorant]

Doesn't matter much to me but it seems to me he was observant Jew. I would tend to believe he didn't stop after the third and meant he wouldn't drink it again after that night. But carry on my wayward son.