True, but how devalued will that payment be for years 31-50. In real terms, it'll be peanuts.

Quite likely. 

Although the savings in monthly payment reaches diminishing returns at some point. Nearly doubling the term (50 vs 30) only produces a ~13% reduction in monthly payment. 



freetx

My expectation is that these will just become the norm and 30-year mortgages will be similarly niche as 15-years are today.