It seems to me that the two sets of research (the famous original testing a child's ability to delay eating a marshmallow in return for another one later and the new data suggesting that children learn such behaviours at home) actually fit well together. The new research merely explains why some children are more prepared to defer gratification; because they come from stable homes where promises are kept. That doesn't make the 1960s Stanford research wrong. Children able to pass the test still do better in life on average because deferring gratification leads to good outcomes. It's just yet another argument for good parenting. Flaky parents tend to raise flaky kids. Duh.
An interesting sidelight is whether governments that constantly change the rules (e.g. generating inflation to cheat their way out of paying their debts in full) affect adult willingness to defer gratification.
Why work hard when the government is going to take the lion's share of what you earn? Why be prudent, when it is going to inflate away the value of your savings, tax such income as they still yield, give the proceeds to the feckless, and manipulate interest rates down to protect over-borrowers and punish savers? The government itself (while the idiot left cries "austerity") is going further into debt at the rate of £2.3 billion a week and encouraging the most indebted consumers in Europe to spend more by way of "stimulus".
Not only is government annoyingly prone to treat us like children but it seems it also behaves like a very flaky parent.