I can’t imagine Bonior coming back to run. He exited in 2002 rather than face Miller (for a quixotic bid for Governor) under the new lines. Getting back to Miller again, it’s unfortunate she passed on 3 opportunities for risk (but high reward) runs (as you cited, the two runs for Senator, but also she resisted entreaties to run early against Bonior in 2000 when the lines favored him, but popularity in statewide office favored her). She did take one “risky” run in 1994 against a past-his-prime Richard Austin for Sec of State, which paid off, but failed to parlay that ever again. It was in 2000 when I actually soured on her a bit when she didn’t take out Bonior when she was able to.
In hindsight, she might’ve been better off running for Governor in 2002 (instead of Lt Gov Dick Posthumus) against the grossly incompetent Jenny Granholm (AKA Grandstand) and spared the state 8 years of that nonsense. She’d likely have been a damn sight better than the squish currently occupying the Governorship, Snyder.
I suppose its possible he'd try to revive his political career, but if Bonior ran again it would remind me of Bob Kerrey's quixotic bid for Nebraska's Senate seat in 2012.