Has anyone considered that Elaine might have said she had a plan when she really didn't have much of one, but was just trying to claim a bit of credit for things working out in the end? (Kind of like Ron Gilbert saying that he wanted to make MI3 but never did, and things worked out for the MI series anyway.)
And I thought TMI was one of the best MI games, Chapter 5 being an exciting and entertaining conclusion to the season. I, for one, am willing to overlook a few questions created by the plot so long as the overall experience was fun and entertaining. In fact, there are a number of extremely popular movies that have been made that, though they have large plothole questions staring you in the face, are still fun and exciting to watch.
As far as Ron Gilbert is concerned, props to the man who created Monkey Island but I believe that though he claims to have had an MI3 game in mind, he never even started creating it. Not to mention that the end of MI2 was full of the weirdness factor that would befit Sam & Max. I personally think that he was just saying that he was planning on making an MI3 himself, just to give himself a bit of props, though the end of MI2 is bizarre and random enough to suggest he never even considered it. Besides, I love Curse. For ages, it was my favorite game (though TMI gives it a run for it's money.)