I don't see a therapist leaving a job as abandonment per se, compared to forced termination or ghosting. What I see as the problem is that your therapists have apparently promised something they couldn't deliver, or you heard it that way. When I've asked my T if he is retiring (he's in his late 60's), he says "I have no plans to retire in the future, but as we know, the future is difficult to predict."

But the fact is that the future is hard to predict, and no therapist should promise to be around forever, if indeed that is what they have said as opposed to what they meant. If I promised someone not to abandon them, like my child, it means (and I've said this) that I will not do something deliberately such as kick him out of the house, refuse to support him emotionally (if not physically) no matter what circumstances he finds himself in, even if I disapprove; or otherwise cut off contact and ghost him. I have said that there may be limits to my desire for contact or support depending on the circumstances (he'll be of legal age soon); he knows that some of my relationships have ended or been limited with certain people in my family-friend network because of mean or exploitive behavior. I don't say things that sound like threats, like if you ever hit me or steal from me, you're outta here. We have a pretty strong and tight relationship and feel those kinds of things are unlikely to happen, but again, can't predict the future.

What I would not see as abandonment is if I decide to move after he leaves for college, if I refuse to let him live in the basement until he's 30, if I refuse to be exploited because of something he wants to do (like be a y o u tube star).

I guess I would wonder, in your shoes, if you are over-interpreting promises of non-abandonment as more than they mean. Otherwise, I don't think T's should make such promises because things can change in an instant with a positive pregnancy test, a need to move because of partner or family relationships, job changes (and T's do a lot of them, IME, moving from community centers to practice groups to private practice and around within each of these choices). No T can promise your insurance will cover them in perpetuity, nor can they promise they won't get sick or die. Nor can they promise they won't quit because they think the therapy is not working.

All they can promise is they will do their best to help you during the time you both agree to work together, and that they will have at least some discussion about the future of your work together. But-- as said in the workplace law-- therapy is an at-will relationships, where it can only proceed if both people want to, and either side can quit at any time. No guarantees, whether you call it abandonment or anything else.