Most of the midwest is losing population except some of the suburbs around the big cities, or certain growth hubs like Dane WI, Washtenaw MI, or Franklin OH.
If anything the suburbs continuing to trend Democratic will be what causes problems for the Republicans with the rural areas losing people.
Yeah. Places like Oakland County, MI do seem to be trending D as places outside metros are becoming more Republican. I kind of doubt though that Democrats will continue to perform as badly as they did outside cities and suburbs in 2016. After the 2004 election, the common narrative was that Democrats are doomed in rural America, but 4 years later, Obama did pretty well in the rural midwest.
And after Goldwater's disastrous campaign in 1964, the GOP recovered magnificently with suburban voters, so I'd say it's very shortsighted to say these trends will continue forever.
Goldwater lost basically everyone.