Just follow what Ford did: throw them at China. Yes the streets are cramped, parking spaces are tiny, highways are congested, but people buy full-size sedans regardless. The XTS/Taurus/Continental are big hits. The middle class millenials grew up seeing 'filthy rich' chauffeured in Cadillacs and Lincolns and now they want their own.You're not kidding. Hyundai Azera is already gone from the U.S. market. Chevrolet Impala is widely expected to die at the end of this generation. Ditto Ford Taurus (although they do have the option of bringing in the newer and different Chinese version). And a recent Bloomberg article suggests that Chrysler 300 and Buick LaCrosse have iffy prospects as well. Perhaps the full-size sedan's future is akin to that of the minivan, as a segment with a diminished but profitable group of players.
I guess that's why some companies still keep their full-size sedan program alive. However most of them just stretch the mid-size sedan, add the mandatory 'L', and call it a day. In fact I believe Lexus should not miss the opportunity to stretch the ES and add a four-seat 'executive' trim to have remote chance of competing against very strong Lincoln/Cadillac/Volvo offerings. If the Camry can have a four-seater version, there's no reason ES couldn't have one.
TBH I was once seriously tempted by the Ford EcoBoost V6s (which are unnecessarily overpowered) because they offer a lot of horsepower and AWD at a bargain. But brand loyalty keeps me waiting for the 7ES till this date.