OT I rather doubt it. At some point, increased square footage becomes divorced from increased utility and is primarily a fashion statement.
There is a strong American Dream meme in the US. Every generation is supposed to aspire to more than their parents had. Do kids really get anything out of soccer + arts + dance + ... as extracurricular? Do we really need more than 2000 sf for a family of 4? No, probably not. But we think we do. That is all it takes.
PS Your opinion that houses will downsize pegs your demographics. In my circles the people under 35 all 'need' 3500 sf, everyone over 55 doesn't understand why any family of 4 needs over 2500 sf.