Lot of people looking way too much into the Grey Matter thing
He brought it up because it was relevant to the situation with Jessie bailing on the meth biz. He's not concerned with those people.
You're right, we probably won't see the biggest thing driving his ego into lunatic choices ever again. His discussion at the restaurant with Gretchen was the first time Walt came out as the angry hurt animal, that I recall, that he has become and seems to be the source feeding his gigantic need for ego. Plus Gilligan said
we'd be hearing about it and learning about it more this season (covered in non-spoilertag posts in the thread earlier), so I don't think you're assessment is accurate. Possible, but not likely IMO.