Stabenow isn’t up until 2018, and Miller passed on the race in 2006 and 2012 despite entreaties from many Republicans ... I doubt that she’ll run.
By which time Miller will be almost 65 (in May 2019), a bit past her prime to be running for a Senate career. We’ve seen how bad it’s been running older candidates for freshman terms (such as Tommy Thompson, running 14 years too late in 2012 when he could’ve taken out a weak freshman, Russ Feingold in 1998).