One thing they didn't take into consideration, is that a lot of boomers had children who are of Generation-X (born 1965-1982). So, it's not a given that the bulk of that $68.4T bill be going to the Millennials. Heck, do they even really lay out what a "Millennial" is? For the longest time it was someone born 1983-2000, although I've seen them play fast and loose with this age range, to fit whatever narrative is being pushed.
Plus, aren't many of the younger boomers still often getting sandwiched in that spot where they're taking care of their aging parents, yet at the same time subsidizing their kids? That's probably going to eat up a lot of that $68.4T.
My parents' generation is mostly older boomers. Dad was born in 1946, Mom in 1949. My stepdad was born in 1952. So was my uncle, who doesn't have any kids, and made me his sole heir. My Dad has two brothers that are are a bit older (1939 and 1940), so they're actually from the "Greatest Generation", although I tend to lump them in with my Mom, Dad, and uncle, since they're of my parents' age range, rather than my grandparents'.
I wonder if there's much of a breakdown in wealth between the older Boomers, which are more likely to have Gen-X kids, and later Boomers, which are more likely to have Millennial kids.
I think the older Boomers might be wealthier, for several reasons. First, their parents were probably a bit more likely to have a good pension, and good health insurance. I know all my grandparents did, so as they aged, got sick and passed away, they didn't run up much in the way of medical bills. And their kids went to college at a time when tuitions were lower, and you didn't have quite the "failure to launch" problem of the kids not leaving the nest. But, the younger Boomers might not be so lucky.
I have a feeling it might be Gen-X that gets the bulk of that $68.4T. Of course, they eventually pass it on to somebody. And again, the older members of that group, will probably pass it on to a Millennial. I didn't have kids, but if I did, it would have been back in the mid 90's, so they would have been Millennials. But a later Gen-Xer probably ended up having an X-ennial, or whatever they're calling the latest bunch.