From what I read the "757-Plus" comments have been widely miss-understood: Boeing is looking at developing a new plane in roughly the same market segment as where the 757 was sitting. They are not looking at restarting the 757 production.

The interim airliner would be an enhanced 767, that is still in production (although not as a passenger aircraft).

Do you have a source for this? I hear this every year and it never happens.

It’s unclear if it happens but it has been mentioned more than once over the last two years.

Is the new aircraft supposed to emerge from the Yellowstone project (Y1)?