It’s not for me to judge somebody’s personal life particularly given that I don’t know any facts. I doubt any of this gossip will affect Miranda much. Interestingly I think it may actually affect Blake a little. There seems to have been a choosing of sides with the Miranda as the heartbroken victim narrative taking hold in many people’s minds. That may change a little.
The effect on Miranda's career is uncertain - but probably depends on what aspect of it is meant. These are only guesses.
I think her Mainstream career is likely to be damaged - but she has seemed to have been moving away from this since her divorce anyway. She's received little radio play in this era, and this publicity (I would think) would make it less likely to recover. The main reasons for that are that radio tends to be controversy-averse, and the "call out" testing tends to catch casual general listeners, rather than dedicated fans of the artist, or the music. It's generally agreed that the "call out" listeners contacted in the Mainstream genre tend towards social conservatism, and may have a particularly negative image of perceived sexual or marital misconduct when it involves a woman. If her recent lack of radio support is mainly attributed to the more off-format style of the music (which has clearly been a factor, but in my view, probably not the only one), I think the latest controversy would make it harder to get back on radio, even if she adopted a more Mainstream-friendly style on a future album. (Bear in mind, too, that she is currently working on a Pistol Annies album, so there would be a likely gap before her next solo album, and an even longer gap since her last significant radio hits - getting back after that would be harder, even without new negative factors.) There have been many signs that radio play has not been her main priority recently, and I think she is repositioning her career, while seeing touring, streaming and her image with less radio-focused music fans as more important.
I think her more Alternative career is less likely to be damaged - and may be enhanced in the minds of people who admire independence, and reject the view of women being required to conform to stricter social conventions than men. A significant number of tweets that I've seen show a backlash against her detractors - these often don't seek to absolve or excuse her, but rather take the view that she doesn't need excusing, and the judgmental hostility (real or ideologically inspired) is the greater problem. For good or bad, marital infidelity has a long history in Country Music, especially (but certainly not exclusively) in the more Outlaw sub genres. To take just a few examples - Johnny Cash and Waylon Jennings both left their wives for women they were touring with - and their new loves - Johnny and June, Waylon and Jessi became "golden couples", iconic parts of the tradition, celebrated in other people's songs. There are also female examples - Tammy Wynnette being particularly noted for entering and leaving a succession of relationships. Something of a record is probably held by Steve Earle, who has been through seven marriages and divorces. I would cite Steve, in fact, as an example of why I, and many others, would put the music first, and the personal frailties a long way behind. This elegy on the death of Townes Van Zandt, filmed at the Bluebird, with Kelly Joe Phelps providing well-judged accompaniment on slide is, for me, one of the great moments in the genre, that brings a lump to my throat whenever I hear it.
I think Miranda's music often leads to similar reactions for many core Country fans - and while things are definitely harder for women today in the Mainstream, that is unlikely to change on the more Alternative fringe.
Finally, there is the question of whether it might affect Miranda's award voting. In that respect, I can't help thinking of the picture she posted earlier this year, of herself in front of a mirror, with the words "I do this thing called whatever I want" scrawled in red, perhaps in lipstick. (This picture was before the present controversy, and can't be directly related to it.) It got a very positive reaction from many fans, who related it to her music, and her attitude to the Mainstream format. The most interesting thing to me, though, was that the photo was tagged as taken by Crystal Dishmon. She is in charge of artist representation and publicity at Shopkeeper Management, and has probably played a significant part in building voting support for Miranda. There are, I think, a couple of ways of interpreting her apparent endorsement of this photo. One is that she didn't see Miranda's assertive and carefree attitude to convention as damaging to her award voting (which seems to have been borne out at the ACM - where Crystal is one of the elected directors - and where Miranda got the double validation for her acclaimed album, following last year's AOTY with this year's SOTY). But the other possibility may be that Crystal was endorsing Miranda's expressed wish to play down awards in general. The photo was posted around the time of the Grammy awards - which Miranda skipped, for the second year running, despite being in New York, going instead, with Crystal, her senior manager and her dress designer to a Broadway show, on what the foursome called a 'Girls Night Out'. Some interpreted this as a protest at the relative lack of female nominees (Miranda herself had been nominated, but concentrated instead on the next night's performance at the Elton John tribute).
The question is - will her award nominations continue, after this negative publicity? Nashville Scene earlier attributed her decade of nominations at the Country shows to an alliance between more critically influenced voters, and those on the more commercially influenced wing who nevertheless vote for music they prefer, rather than for what their label prefers. Again, I can only guess, but my feeling is that some of that voting on the more commercial side will now break away, and the ACM voting may prove to have been a peak - and that Miranda's management are foreseeing that. (But this is a notoriously uncertain area to predict)