I think this is one of those questions where the answer is so client dependent that there isn’t one right answer. I’ll answer it for myself but my answer won’t necessarily be right for everyone.
The only reason I can imagine for me ending therapy with my current therapist early is if it became clear to both of us that we’d reached some kind of hard limit where I’d made as much progress as I possibly could with him and he wouldn’t be able to take me further but I still needed to grow more. By the time it got to that point he and I would have tried a number of different things and come up unsuccessful each time. It would be a very mutual decision that the only way forward for me would be for he and I to part ways in terms of my therapy.
And yes, I think if that happened, we would both feel very sad and yes, I would want him to show me. The sadness wouldn’t change the decision, but would probably make for a tearful goodbye.
I’d also want to see and experience the hope for my future work as well as the love that was willing to let me go.